Latest ESO telbib papers

Dust characterization of halos: The extended emission in protoplanetary disks

First Author: Das, Sreejita
Instruments: ALMA_Band_3, ALMA_Band_6, ALMA_Band_7, ALMA_Band_8, ALMA_Band_9
ProgramIDs: 2017.1.01460.S, 2018.1.01119.S, 2018.1.01755.S, 2019.1.00837.S, 2016.1.00565.S, 2013.1.00798.S, 2013.1.00226.S, 2013.1.00694.S, 2013.1.00498.S, 2021.1.00378.S, 2021.1.00879.S, 2019.1.01760.S, 2021.1.01123.L, 2019.1.01357.S, 2018.1.01055.L, 2018.1.01198.S, 2017.1.01330.S, 2016.1.00484.L
BibCode: 2026A&A...710A.238D

Context. Extended low surface brightness emission has been identified in a number of protoplanetary disks, in tension with predictions of radial drift theory. Aims. We aim to investigate the nature and origin of faint, extended dust emission in the outer regions of protoplanetary disks, which we define as the "Halo", using multiwavelength (sub)millimeter continuum observations of three systems: Elias 2─24, IM Lup, and DM Tau. Methods. We utilized Atacama Large Millimeter Array (ALMA) observations of our targets to perform spectral energy distribution (SED) fitting with four dust compositions and derived radial profiles of their dust properties. Results. The halos identified in our sources account for 20─30% of the total flux density at (sub)millimeter wavelengths. In Elias 2-24, IM Lup, and DM Tau, we infer maximum grain sizes of 2 cm, <4 mm, and <9 mm, with the data best reproduced by porous amorphous carbon, compact amorphous carbon, and compact organic carbon compositions, respectively. Their total dust masses are 125₋₂₃⁺³⁴, 301₋₁₀₁⁺¹³⁹, and 829₋₃₇₈⁺⁷⁶¹ M_⊕, with corresponding halo masses of 33₋₆⁺¹², 103₋₁₇⁺²⁵, and 316₋₁₁₇⁺²⁰² M_⊕. The halos of IM Lup and DM Tau are dust rich with gas-to-dust mass ratios of 64 and 18, respectively. In all three disks, the dust drift and growth timescales are shorter than the disk ages, implying that the smooth outer disks should not exist. Conclusions. The halos in our sources hold relevant fractions of the total dust reservoir, demonstrating that they play an important role in alleviating the mass-budget problem. While the persistence of halos in IM Lup and DM Tau could be explained by late infall, the presence of centimeter-sized grains in Elias 2-24's halo suggests that unresolved dust traps also play a role.

The Radial and Vertical Structure of Molecular Gas in the Edge-on Galaxy NGC 4565

First Author: Krahm, Grace
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.01050.S
BibCode: 2026AJ....172...50K

We present high-resolution (0 .″ 94 ≍ 55 pc) Atacama Large Millimeter/submillimeter Array (ALMA) CO(2─1) and¹³CO(2─1) observations of the highly inclined ( i∼87.°5 ) galaxy NGC 4565 covering out to galactocentric radius R_gal ≳ ± 17 kpc. The combination of sensitivity and resolution enables the detection of CO emission well into the H I-dominated outer disk while isolating individual molecular clouds across the full extent of the galaxy. Although often described as an edge-on Milky Way analog, the molecular gas profile of NGC 4565 has a central gap that is more similar to M31. The ¹³CO/¹²CO ratio remains consistent at 0.086 ± 0.009 from R_gal = 5─13 kpc. Based on fits to position─velocity slices, the molecular disk remains thin, with an FWHM scale height of 79.1 ± 1.6 pc measured from the vertical intensity profile with little evidence for vertical flaring. Molecular clouds in NGC 4565 show sizes, linewidths, and surface densities consistent with those found in similar environments in PHANGS-ALMA galaxies and in M31. We identify a prominent star-forming complex on the ring—an overdensity of molecular gas we term the "East Ring Pileup." This feature hosts a compact, multiwavelength-bright region, which we call "the Jewel." Effects of galaxy inclination on molecular cloud radius, velocity dispersion, surface density, and virial parameter appear as second-order effects that are strongest in velocity dispersion. At this resolution, GMCs are preferentially aligned with the disk of the galaxy and horizontally elongated by a factor of ∼2.

Joint Rossiter-McLaughlin Revolutions analysis of the multi-planetary system GJ 9827

First Author: Fridén, E.
Instruments: ESPRESSO
ProgramIDs: 1102.C-0744, 110.24CD, 108.2254
BibCode: 2026A&A...710A.242F

GJ 9827 is a compact system hosting three close-in planets in near-resonant orbits that span the radius gap, a deficit of close-in planets separating super-Earths and mini-Neptunes. We analysed transit observations from the ESPRESSO GTO program acquired on each planet and performed a joint Rossiter-McLaughlin (RM) analysis of the three planets using the ANTARESS workflow. We measured the sky-projected spin-orbit angle of each transiting planet (λ_b = 9₋₆₄^+67°, λ_c = −21₋₄₄^+43°, and λ_d = −1 ± 26°) and found them, within uncertainties, to be consistent with an alignment with the stellar spin axis. These results, derived with the RM Revolutions technique, are fully compatible with a classical analysis of the RM anomaly. By combining information on the stellar radius and rotation period, we derived the true 3D spin-orbit angles. Our results indicate that the star is viewed equator-on, with 3D spin-orbit angles of Ψ_b = 54₋₃₈^+26°, Ψ_c = 46₋₃₀^+22°, and Ψ_d = 33₋₂₄^+16°. The 3D spin-orbit angles are broadly consistent with a coplanar system but remain weakly constrained, with posterior distributions peaking at moderate misalignments. An aligned architecture remains compatible at the 2 σ level. These findings support a scenario of smooth disc-driven migration for the three planets, potentially allowing for a moderate primordial misalignment between the protoplanetary disc and the stellar spin axis. Further observations are encouraged to confirm these conclusions.

Planet engulfment in the chemically anomalous HD 129171/HD 129209 pair

First Author: Rathsam, Anne
Instruments: UVES
ProgramIDs: 113.26GJ
BibCode: 2026A&A...710A.236R

Context. Binary systems composed of stars with similar parameters are expected to have identical chemical composition. However, many chemically anomalous pairs have been found in the literature, such as the binary HD 129171/HD 129209. It is still unclear whether these anomalies originate from inhomogeneities of protostellar clouds, with important implications for chemical tagging and theories of star formation, or if they are caused by a planet engulfment event suffered by one binary component. Aims. In this work, we measured precise differential abundances for the system HD 129171/HD 129209 to explore the planet engulfment hypothesis proposed in the literature. We focused on the Be abundance in particular, showing that this element can serve as a diagnostic of engulfment events for solar-type stars. Methods. Atmospheric parameters were determined imposing spectroscopic equilibrium of iron lines. Masses and ages were estimated with the isochronal method. The Li, Be, N, and O abundances were determined via spectral synthesis. Other elemental abundances (up to Zn) were determined by equivalent width measurements. The spectra adopted in the analysis was gathered using UVES/ESO. Results. We confirm the large difference in [Fe/H] (0.120 ± 0.004 dex) and A(Li) (−1.00 ± 0.02 dex) among the members of the pair, as well as the trend between differential abundances and condensation temperature of the elements. The binary system also shows detectable differences in Be abundances (−0.20 ± 0.04 dex). The abundance pattern of the pair is reasonably reproduced by an engulfment model of 11.2 M_⊕ of rocky material. Conclusions. The difference in chemical abundances of the HD 129171/HD 129209 pair provides strong evidence in favor of the planet engulfment scenario. In this context, the detection of a Be difference among chemically inhomogeneous binary systems can be used as a diagnostic of rocky material ingestion experienced by a member of the pair.

Connecting CGM enrichment with Lyman α emitters at 2.9 < z < 6.7

First Author: Sebastian, Alma Maria
Instruments: MUSE
ProgramIDs: 106.215A, 095.A-0714, 0103.A-0140
BibCode: 2026MNRAS.549ag954S

We present the results of a blind search for Lyman

$\alpha$

emitters (LAEs) in three deep archival

$z\sim 6$

quasar fields from VLT/MUSE using state-of-the-art detection algorithms. We explore their connection with absorbers ─ particularly C IV and Mg II ─ in the circumgalactic medium (CGM) from the E-XQR-30 (Enlarged Ultimate XSHOOTER Legacy Survey of Quasars) survey. We detect 156 LAEs at

$2.9\lt z\lt 6.7$

with luminosities ranging from log

$L[\rm{erg\,s}^{-1}]=$

41.3 to 43.2. We find 34 and 14 galaxy associations with C IV and Mg II absorption, respectively, at

$3.4\lt z\lt 5.8$

within a line-of-sight velocity window of

$\pm 1000~\text{km}^{-1}$

and impact parameter of

$\lt 250$

pkpc. These systems have a weak anticorrelation with respect to the absorber strength-impact parameter relation. No Mg II systems are found within the virial radii of any LAE, while four C IV absorbers are located within the virial radii of an LAE suggesting that low ionization gas has a lower covering fraction. The LAEs have mild overdensity ratios of 1.7 and 1.9 around C IV and Mg II, respectively. The stellar mass upper limits of

$\text{log}~M_*\lt 10.7~\text{M}_\odot$

estimated using Keck/NIRC2 imaging indicate that a low-mass, faint population of galaxies pollutes the CGM with metals. This paper serves as a pilot analysis for the forthcoming REQUIEM survey, an ESO Large Program on high-redshift deep quasar fields.

Fast, dust-poor outflows in the local candidate dual AGN MCG-03-34-64 observed with VLT/ERIS

First Author: Lamperti, I.
Instruments: ERIS, XSHOOTER
ProgramIDs: 0102.A-0433, 113.26BW
BibCode: 2026A&A...710A.193L

We present VLT/ERIS integral field unit (IFU) J-band observations of MCG-03-34-64, a nearby (z = 0.0167) Seyfert galaxy hosting a candidate dual active galactic nucleus (AGN) system with a separation of ∼100 pc between the nuclei, which are detected in Fe-Kα X-ray images and [O III]λ5007Å narrow-band images. The ERIS observations cover, among others, the He Iλ1.083μm, [Fe II]λ1.257μm, and Paβ emission lines, over a field of view of 3″ × 3″ (∼1 × 1 kpc²). We analysed the ionised gas kinematics and identified two regions with an enhanced velocity dispersion (W80 ∼ 1500 km s⁻¹), which is suggestive of fast outflowing gas, spatially coincident with the position of the two candidate active nuclei. We extracted the spectra from the two regions and used them to derive the properties of the ionised outflows. The two spectra show a prominent blueshifted wing with velocities v_max ∼ −1700 km s⁻¹, which corresponds to the highest 2 − 5 percentiles of samples of local AGN with similar bolometric luminosities (∼10⁴⁴ erg s⁻¹). For the ionised phase of the two outflows, we derive comparable masses of ∼(4 ± 1)×10⁵ M_⊙ and mass outflow rates of ∼20 ± 5 M_⊙ yr⁻¹. The two distinct outflows could be associated with the two nuclei or be generated by the interaction of the radio jet with the interstellar medium (ISM). The map of the [Fe II]/Paβ line ratio shows the highest values in the more external regions (compatible with shock excitation), intermediate values in the vicinity of the nuclei (compatible with AGN excitation), and lower values between the two nuclei, close to the peak of the optical and near-infrared continuum. We interpret this as due to a contribution to the Paβ emission from a nuclear starburst or to enhanced AGN ionisation. We also analysed the peculiar (very broad, boxy) profile of the [Fe VII]λ6087Å optical coronal line from an archival VLT/X-shooter spectrum. The comparison with the [Ne V]λ3425Å and [Fe II]λ1.257μm profiles indicates that [Fe VII] emission likely arises only from the outflow. The absence of the systemic component in [Fe VII] ─ unlike in [Ne V], which has similar ionisation potential and critical density ─ suggests suppression of [Fe VII] due to iron depletion onto dust grains, while its detection in the outflow implies a lower dust content than in the host ISM. The additional information gained from the ERIS data are consistent with the scenario of a dual AGN, however, further observations are required to confirm its nature.

Decomposing cool stellar populations with H-band spectral fluctuations: long-period variable stars in NGC 5128 and carbon stars in NGC 5102

First Author: Smith, Russell J.
Instruments: ERIS
ProgramIDs: 115.28DN
BibCode: 2026MNRAS.549ag994S

We analyse new H-band integral-field unit observations of two galaxies at

$\sim$

4 Mpc, using a principal components analysis of pixel spectra to probe their giant star content. In both galaxies, the signals arise in near-resolved point-like sources without large-scale variation, consistent with each pixel sampling stars randomly from a common underlying population. In the (mostly) old bulge of NGC 5128, the observed pixel-to-pixel variation is dominated by a component with a mid-M giant spectrum with prominent CO bandheads. We also recover a smoother second spectral component, apparently driven by contributions from later spectral types. This component is not present in predictions from Poisson-sampled models of old stellar populations; we suggest that it arises from the cool phases of long-period variable stars. (An appendix provides direct evidence for such variables in complementary two-epoch MUSE observations.) In the contrasting galaxy NGC 5102, where a post-starburst stellar population is known to be present, we again find two distinct components. As before, the first component carries the CO bands typical of M-giants. The second eigenspectrum in this younger galaxy shows a strong 1.77

$\mu$

m C

$_2$

bandhead, a feature which is characteristic of carbon stars. Our results highlight the ability of integral field data to access information beyond the total spectrum, even when individual stars cannot be classically resolved.

ULTIMATE Deblending. I. A 50-band Ultraviolet to Mid-infrared Photometric Catalog Combining Space- and Ground-based Data in the JWST/PRIMER Survey

First Author: Sun, Hanwen
Instruments: VIRCAM
ProgramIDs: 179.A-2005, 198.A-2003, 110.25A2, 1104.A-0643, 284.A-5026
BibCode: 2026ApJS..285....1S

Our understanding of the early Universe has long been limited by biased galaxy samples selected through various color criteria. With deep JWST infrared imaging, mass-complete galaxy samples can now be studied up to z ∼ 8 for the first time. However, recent work has revealed systematic uncertainties in measuring the physical properties of galaxies based solely on JWST/NIRCam and Hubble Space Telescope (HST) photometry, due to their limited wavelength coverage. This highlights the need for supplementary data, particularly in the rest-frame UV and near-infrared. Here we present the ULTIMATE-deblending project, which will eventually deliver self-consistent UV to radio photometry for galaxies detected in deep JWST surveys, including both NIRCam and MIRI data. In this first paper, we release a 50-band photometric catalog spanning CFHT U to JWST/MIRI F1800W, covering a total of 627.1 arcmin² across two JWST/PRIMER fields. We detail the reduction of the JWST imaging data, the photometric procedures, and the spectral-energy-distribution-fitting methodology used to derive the galaxy properties. Compared with photometry including only HST and JWST bands, the inclusion of deblended low-resolution photometry from ground-based telescopes improves the accuracy of photometric redshifts by ∼40%, while reducing the outlier fraction by ∼60%. This galaxy sample can serve as a key reference for statistical studies of galaxy formation and evolution in the early Universe. All catalogs and JWST mosaics from the ULTIMATE-deblending project have been made publicly available.

The VMC survey: LV. The coherent expansion of the SMC

First Author: Vijayasree, S.
Instruments: VIRCAM
ProgramIDs: 109.231H, 0103.B-0783, 105.2042, 0103.D-0161, 179.B-2003, 099.D-0194
BibCode: 2026A&A...710L..20V

Context. The Small Magellanic Cloud (SMC) exhibits significant kinematic disequilibrium due to interactions with the Large Magellanic Cloud (LMC). Aims. Here, we investigate the two-dimensional stellar kinematics of the SMC to understand the dynamical effects of these interactions by exploiting the increased time baseline of 6−11 years from the VISTA Survey of the Magellanic Clouds (VMC) data release 7. Methods. We derive proper motions with a threefold improvement in precision compared to previous studies based on VMC data. We used a geometric framework accounting for perspective effects from line-of-sight motion to model the systemic motion across the SMC and construct a residual proper motion map. We further introduce an anisotropic linear velocity gradient model to quantify the stretching of the galaxy. Results. For the first time across all stellar populations, the residual proper motion map reveals expansion along the south-east and north-west directions, consistent with LMC-induced tidal forces, detectable even in the central regions. The gradient-corrected residuals show predominantly radial motions towards the SMC centre with no evidence of rotation. Velocity maps for different stellar populations, without assuming a rotating-disk model, reveal a coherent northward motion away from the centre exclusively in older red giant branch stars, interpreted as a kinematic signature of a past (> 2 Gyr ago) interaction. Conclusions. This study highlights the inadequacy of simple rotating-disk models in capturing the internal kinematics of the galaxy.

NGC 1647: A young open cluster with a broad main sequence observed with LAMOST

First Author: Frasca, A.
Instruments: UVES
ProgramIDs: 0102.C-0040
BibCode: 2026A&A...710A.164F

Aims. In this work we present the results of our analysis of medium-resolution LAMOST spectra of candidate members of the cluster NGC 1647 with the aim of determining the stellar parameters, activity level, lithium abundance, and to study the cluster properties. Methods. We used the code ROTFIT to determine the atmospheric parameters (T_eff, log g, and [Fe/H]), radial velocity (V_r), and projected rotation velocity (v sin i). Moreover, for solar-type and cooler stars (T_eff≤ 6500 K), we calculated the Hα and Li Iλ6708 net equivalent width by means of the subtraction of non-active photospheric templates. We determined the rotation periods for 160 stars by analyzing the available TESS photometry. Results. We derived V_r, v sin i, and atmospheric parameters for 341 spectra of 155 stars, plus three additional bright targets with archival UVES spectra. Moreover, we found four double-lined spectroscopic systems for which we provide the radial velocities of the two components. The V_r distribution of the cluster members peaks at −5.3 km s⁻¹ with a dispersion of 1.6 km s⁻¹, while the average metallicity is [Fe/H] = −0.08±0.08 dex, in line with previous determinations, which were based on only a handful stars. From the fitting of the spectral energy distribution of 160 likely members we infer the existence of a differential reddening across the cluster field with an average value of A_V = 1.1 mag. The A_V values show a distinct correlation with the color offset from the lower boundary of the main sequence, as observed in the Gaia color─magnitude diagram; conversely, this offset appears to be uncorrelated with v sin i. These two findings confirm that differential reddening is the primary driver behind the observed extended main-sequence turnoff (eMSTO) in this cluster. The age of NGC 1647, obtained from the lithium abundance, is 203±27 Myr, which is compatible with the values inferred from a gyrochronological approach and the isochrone fitting.

An ultra-short-period super-Earth and a sub-Neptune orbiting the K dwarf TOI-4311

First Author: Eschen, Yoshi Nike Emilia
Instruments: HARPS
ProgramIDs: 111.254R
BibCode: 2026MNRAS.549ag952E

We report the discovery and characterization of the multiplanetary system around TOI-4311, a K dwarf kinematically between the Galactic thick disc and Hercules stream. TOI-4311 hosts an ultra-short-period super-Earth (P

$\sim$

0.99 d,

$1.376^{+0.077}_{-0.080}$

$_{\oplus }$

) and a longer period sub-Neptune (P

$\sim$

15 d,

$2.47^{+0.12}_{-0.11}$

$_{\oplus }$

) that was first detected in the Transiting Exoplanet Survey Satellite photometry. Using follow-up observations with CHaracterising ExOPlanet Satellite and High Accuracy Radial Velocity Planet Searcher (HARPS), we refine the planetary radius of both planets, derive the mass of planet b (

$4.5^{+1.5}_{-1.4}$

$_{\oplus }$

), and confirm the planetary nature of planet c. Intriguingly, a third periodic signal is clearly detected in our HARPS Radial Velocities (RVs) that we cannot link to stellar activity. This signal could be attributed to a third planet (P

$\sim$

38 d, Msin(i) =

$26.4^{+6.3}_{-6.8}$

$_{\oplus }$

) in the system; however, with the current photometric data set we do not find a transit. Our dynamical analysis highlights that this potential outer planet would remain stable. Using the precise radius and mass for TOI-4311 b, we model its interior structure and find that it is very dense given the host star's galactic kinematics and chemistry. Hence, this system could challenge current formation theories and provide insights into planet formation across the galaxy.

MAUVE─MUSE: when metallicity follows or fights star formation ─ a mass-dependent inversion in Virgo galaxies

First Author: Huang, Rongjun
Instruments: MUSE
ProgramIDs: 105.208Y, 110.244E
BibCode: 2026MNRAS.549g1019H

Although globally integrated studies often find that, at fixed stellar mass, high star formation rate (SFR) galaxies are relatively metal-poor while lower SFR systems are more metal-rich, the corresponding coupling between gas-phase metallicity (

$Z_{\rm gas}$

) and star formation on sub-galactic scales remains poorly constrained. In this study, we analyse 14 Virgo spiral galaxies from the MAUVE─MUSE (Multiphase Astrophysics to Unveil the Virgo Environment with MUSE) survey to revisit the resolved mass─metallicity relation (rMZR) and its secondary dependence on SFR surface density (

$\Sigma _\mathrm{SFR}$

) at

$\sim 100$

pc scales. We construct cospatial maps of stellar mass surface density (

$\Sigma _*$

$\Sigma _\mathrm{SFR}$

and gas-phase oxygen abundance. MAUVE─MUSE galaxies follow a standard rMZR, but once binned in

$\Sigma _*$

, we find a clear mass-dependent inversion in the

$Z_\mathrm{gas}$

─

$\Sigma _\mathrm{SFR}$

relation with O₃N₂-based metallicity calibrations: the commonly reported anticorrelation is confined to low-

$\Sigma _*$

bins, whereas high-

$\Sigma _*$

regions show a positive correlation, with an inversion point at

$\log _{10}(\Sigma _*/\mathrm{ M}_\odot \, \mathrm{kpc}^{-2})\simeq 7.5$

─8.0. Both correlated and anticorrelated H II regions can co-exist within the same discs, and the observed mass dependence emerges only when grouping H II spaxels by

$\Sigma _*$

. We develop a spatially resolved gas─regulator model and show that the observed correlation and anticorrelation between

$Z_\mathrm{gas}$

and

$\Sigma _\mathrm{SFR}$

arise from the competition between star-formation- and gas-supply-driven variability: the sign of the local

$Z_\mathrm{gas}$

─

$\Sigma _\mathrm{SFR}$

relation is set by which of these dominates. This framework can be naturally extrapolated to the integrated scenario, providing a unified explanation for both the resolved and global

$Z_\mathrm{gas}$

─

$\mathrm{SFR}$

relations. However, the presence and strength of the

$Z_\mathrm{gas}$

─

$\Sigma _\mathrm{SFR}$

(anti)correlation depend strongly on the metallicity indicator used, highlighting the challenge of disentangling physical secondary trends within metallicity scaling relations.

Spectral Disentangling Reveals Deep CNO-cycle Exposure in ET Cru

First Author: Yucel, Gokhan
Instruments: FEROS
ProgramIDs: 086.D-0236
BibCode: 2026AJ....172...15Y

Binary stars undergoing mass transfer provide unique laboratories for testing stellar evolution. Here, we present a comprehensive photometric and spectroscopic analysis of the semidetached system ET Cru. Using spectral disentangling, we independently determined the effective temperatures and chemical abundances of both components with high precision, including nine elements (11 species). We find masses of 13.41 M_⊙ and 6.00 M_⊙ for the primary and secondary, respectively, with uncertainties of only ∼1.3%. The radii are 5.58 R_⊙ and 5.68 R_⊙, measured to within 0.4% and 0.5%. Surface gravities are constrained to better than 1%, while effective temperatures are determined to within 3%─5%. The secondary exhibits extreme chemical anomalies, with severe carbon depletion and nitrogen enrichment far exceeding those reported in classical Algol systems. Multiwavelength spectral energy distribution modeling yields a distance of ∼2.5 kpc, inconsistent with the Gaia DR3 parallax, suggesting systematic astrometric uncertainties in the parallax distance. Together, these results establish ET Cru as a benchmark Algol-type binary, revealing direct spectroscopic evidence of deep CNO-cycle exposure in the donor and confirming the primary star as a rejuvenated gainer. ET Cru thus provides a chemically and dynamically illustrative case for understanding advanced binary interactions and the late evolutionary stages of massive-star evolution.

Gaia FGK benchmark stars: Selecting infrared lines for abundance determination

First Author: Elgueta, S.
Instruments: CRIRES
ProgramIDs: 109.234G, 108.22KH
BibCode: 2026A&A...710A.111E

The advent of new and more powerful infrared spectrographs has significantly motivated the advancement of the study of atomic and molecular line lists and stellar atmosphere models. While optical abundance determinations rely on extensively validated line lists and modeling frameworks, infrared measurements still face comparatively larger uncertainties, largely driven by the choice of atmospheric models and the quality of the available atomic data. In this work, we aim to deliver a homogeneous and reproducible set of atomic absorption lines in the Y, J, and H bands (9800─18 000 Å) based exclusively on laboratory atomic data. We analyzed CRIRES spectra of six Gaia FGK benchmark stars spanning a wide range in effective temperature, surface gravity, and chemical composition. Synthetic spectra were computed using the benchmark stellar parameters, and each transition was evaluated independently in every star through a quantitative sequence that examines line depth, saturation, blending (purity), and the agreement between observed and synthetic line profiles. We identified a set of robust atomic transitions in these bands that remain consistent across the full range of stellar parameters represented in our sample. Lines of α-elements such as Mg I, Si I, and Ca I, together with several Fe I transitions, satisfy all robustness criteria. Among the neutron-capture species explored, only Sr II provides lines that consistently meet our requirements. Beyond the specific list of accepted transitions, this study demonstrates that a fully quantitative multi-criteria framework provides a transparent and reproducible foundation for near-infrared line validation as laboratory data, stellar atmosphere models, and instrumentation continue to improve.

Gaia21bja: Pre-main-sequence Star with Quasiperiodic Bursts

First Author: Mátéfy, Ádám
Instruments: XSHOOTER
ProgramIDs: 112.25XA
BibCode: 2026ApJ..1004..142M

Gaia21bja is a Gaia alerted young stellar object (YSO) that exhibits at least seven quasiperiodic brightenings over a 20 yr long light curve with durations of 1.5─2 yr and amplitudes up to ∼1.7 mag in the Gaia G band. We analyze its optical and near-infrared photometry and spectra taken using the Infrared Telescope Facility and Very Large Telescope in its faint and bright states in order to characterize its physical properties. A Lomb─Scargle periodogram analysis results in the most significant period of 916 ± 77 days. We derived the stellar parameters as R_⋆ = 0.78 ± 0.04 R_⊙, L_⋆ = (4.5 ± 0.3) × 10⁻² L_⊙, and M_⋆ = 0.16 ± 0.03 M_⊙. The spectra taken during the burst are dominated by emission lines and are similar to those of EX Lupi-type eruptive young stars (EXors). We found that the accretion luminosity and mass accretion rate increased by a factor of 5.5─6 during the burst. Based on this, and the quasiperiodic bursts, we suggest that Gaia21bja is an eruptive YSO, and is most consistent with the "Periodic" category of the Outbursting YSOs Catalogue.

TYC 170─1218─1: A new r-process-enhanced extremely metal-poor star, rich in Th.

First Author: Caffau, E.
Instruments: UVES
ProgramIDs: 112.25EH
BibCode: 2026A&A...710A.132C

Context. Extremely metal-poor (EMP) stars are formed from gas clouds enriched by one or a few supernova explosions belonging to the first stellar generation and this very limited number of sources of metal enrichment is suitable to produce peculiar chemical patterns that give birth to stars with anomalous chemical composition. Among the EMP stars, r-II stars are characterised by an over-abundance of the heavy elements with respect to iron. Aims. In the search for apparently young, metal-poor stars, we serendipitously selected TYC 170─1218─1, which turned out to be an EMP star, enhanced in neutron capture elements over iron. Our aim is to obtain a detailed chemical inventory for this exceptional object. Methods. We investigated high-resolution spectra observed with UVES at the VLT telescope and Mike at the Magellan Clay telescope. We derived the abundance of 33 elements using the MyGIsFOS code and an ATLAS 9 model atmosphere. Results. The star is an EMP with [Fe/H]=−3.52. It is enhanced in the α elements, as EMP stars usually are. It is an r-II star with [Eu/Fe]=+1.84 and [Th/Fe]=+1.85. The star is also poor in carbon with respect to iron. The quality of the spectra was insufficient for us to detect uranium. Kinematically the star belongs now to the Galactic halo, but it joined the Milky Way during the Sequoia accretion event.

Detection of a large-scale organized 2 kG order magnetic field in the Herbig Ae star HD 179218

First Author: Jarvinen, S. P.
Instruments: HARPS
ProgramIDs: 109.230J, 115.27WZ
BibCode: 2026A&A...710L..13J

Context. While about two dozen Herbig Ae/Be stars have been reported to be magnetic, only two of them, HD 101412 and HD 190073, have had their magnetic field geometries studied in the past. The knowledge of the magnetic field structure is important to understanding how magnetospheric accretion works in these stars. Aims. We aim to study in detail the spectral and magnetic variability of HD 179218, which is necessary to put constraints on its magnetic field geometry. Methods. We measured the mean longitudinal magnetic field, ⟨B_z⟩, from newly acquired and archival high-resolution spectropolarimetric observations of HD 179218 using the least-squares deconvolution technique. Additionally, we studied the spectral variability of the hydrogen lines using dynamical spectra. Results. Based on our analysis of the Stokes V spectra of HD 179218, we report for the first time the definite detection of a magnetic field. Using a slightly refined rotation period of P_rot = 1.34102 d, we constrained its geometry as follows: an estimated magnetic obliquity angle of β = 79.9 ± 0.7° and a dipole strength of B_d = 2142 ± 52 G. The ⟨B_z⟩ variation is best fitted by the superposition of a sine wave and of its first harmonic, but more spectropolarimetric observations are necessary to test the impact of the limited measurement precision and the uneven coverage of the rotation cycle. The strongest emission in the Hα and Hβ line profiles in the medium-resolution spectra acquired in 2025 was detected close to the phases of the best visibility of the magnetic poles. HD 179218 is the second Herbig Ae/Be star after HD 190073 for which a first snapshot of a magnetosphere is presented.

MAUVE─MUSE: Ionization and Kinematic Signatures of Environmental Effects on Virgo Cluster Disks

First Author: Brown, Toby
Instruments: MUSE
ProgramIDs: 110.244E
BibCode: 2026ApJ..1004...73B

We present early science results from the Multiphase Astrophysics to Unveil the Virgo Environment (MAUVE) program, which targets 40 Virgo Cluster galaxies to investigate the effect of environment on the interstellar medium (ISM) at ∼100 pc scales. From 12 galaxies in the MAUVE─Multi Unit Spectroscopic Explorer (MUSE) early sample, we find systematically elevated line ratios compared to Physics at High Angular resolution in Nearby GalaxieS (PHANGS)─MUSE field disks, with higher medians of [N II]/Hα (0.75 versus 0.50), [S II]/Hα (0.57 versus 0.49), and [O III]/Hβ (1.04 versus 0.68). Spatially resolved Baldwin─Phillips─Terlevich diagrams show 74% of MAUVE spaxels ionized by sources other than H II regions versus 61% in the field, and we find these ionization differences to be closely coupled to broadened kinematics. In all, 44% of MAUVE spaxels exceed Hα σ_LOS = 40 km s⁻¹ (versus 26% in the field), driven mainly by non-star-forming gas with σ_LOS between 40 and 80 km s⁻¹, consistent with enhanced contribution of diffuse ionized gas (DIG). A subdominant tail of 5% of spaxels at σ_LOS > 100 km s⁻¹, largely absent in PHANGS─MUSE (1%), points to shocks or turbulent mixing layers from intracluster interactions. Our results show that environmental quenching primarily suppresses star formation, unveiling DIG as the dominant ionized component in cluster disks. The elevated line ratios and broadened kinematics observed in the MAUVE sample reflect the physical state of the ISM in the absence of vigorous star formation, rather than widespread direct environmental excitation. The observed shock-like emission provides an additional, secondary contribution likely driven by active interactions with the intracluster medium.

JOYS: Linking the molecular ice and gas phase composition toward the high-mass hot core IRAS 18089─1732

First Author: Gieser, C.
Instruments: ALMA_Band_3
ProgramIDs: 2018.1.00424.S
BibCode: 2026A&A...709A.235G

Context. The formation and destruction of molecules in the interstellar medium involve a complex interplay between gas phase reactions, as well as processes on grain surfaces and within icy mantles. In recent decades, the gas phase composition of the cold material toward star-forming regions could be well characterized using (sub)millimeter facilities. Prior to the launch of the James Webb Space Telescope (JWST), ice species other than the main constituents (i.e., H₂O, CO, CO₂, NH₃, CH₄, and CH₃OH) were challenging to detect due to insufficient sensitivity as well as angular and/or spectral resolution. Aims. We aim to determine molecular ice and gas phase column densities toward the young and embedded high-mass hot core IRAS 18089-1732 within a region of 5000 au. Methods. We used spectroscopic data from 5 to 28 μm obtained with JWST to derive the ice column densities of H₂O, SO₂, OCN⁻, CH₄, HCOO⁻, HCOOH, CH₃CHO, CH₃COOH, C₂H₅OH, CH₃OCH₃, and CH₃COCH₃. We inferred the gas phase column densities for a total of 38 molecules, including O-, N-, S-, and Si-bearing species, as well as less abundant isotopologs, from sensitive molecular line observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) at 3 mm wavelengths. Results. We find comparable abundances (relative to C₂H₅OH or CH₃OH) in both phases for C₂H₅OH, CH₃OH, and CH₃OCH₃. The abundances of SO₂ and CH₃COCH₃ are higher in the gas phase, suggesting additional gas phase formation routes. The abundance of CH₃CHO is one order of magnitude higher in the ices compared to the gas phase. The ice abundances (relative to H₂O ice) toward the IRAS 18089 hot core are similar to previously studied Galactic low- and high-mass protostars. There are hints of a decreasing abundance with galactocentric distance for OCN⁻, CH₃OH, and CH₃CHO ices. Conclusions. It is evident that not all species show comparable abundances in the ice and gas phases. However, we do find similar trends when species show elevated ice or gas phase abundances in the high-mass hot core IRAS 18089, compared to low-mass hot cores. To better understand the reaction pathways of molecular species, statistical surveys analyzing both the ice and gas phase chemical composition of high- and low-mass protostars at different Galactocentric radii are essential.

First Interstellar Detection of Methyl Carbamate: A New Observational Anchor for Glycine Chemistry

First Author: Duan, Chunguo
Instruments: ALMA_Band_7
ProgramIDs: 2019.1.00768.S
BibCode: 2026ApJ..1004L...6D

Glycine—the simplest amino acid—has remained undetected in the interstellar medium despite decades of sensitive searches, motivating alternative approaches to constrain its astrochemical origin. A promising strategy is to investigate the broader C₂H₅O₂N isomer family and identify detectable members that can serve as observational anchors for glycine-related chemistry. Herein, we report the first robust interstellar detection of methyl carbamate toward the hot molecular core G358.93-0.03 MM1 using Atacama Large Millimeter/submillimeter Array 1 mm observations. Ten unblended rotational transitions are identified, yielding a column density of (4.2 ± 0.8) × 10¹⁵ cm⁻² and an excitation temperature of 204 ± 10 K. We also searched for other C₂H₅O₂N isomers with available rotational spectroscopic data, including glycine, but none were detected, allowing us to derive upper limits on their column densities. The resulting abundance pattern deviates significantly from the minimum energy principle predictions, highlighting that the C₂H₅O₂N family is shaped primarily by kinetic chemical processes rather than thermodynamic equilibrium. The observed methyl carbamate abundance is consistent with a grain-surface formation scenario involving radical─radical recombination (CH₃O + NH₂CO), further supported by its correlated abundances with its proposed precursors, methanol and formamide, across diverse astrophysical environments. This detection establishes methyl carbamate as a new observational anchor for glycine chemistry, providing critical constraints on the formation pathways of amino-acid-related molecules in star-forming regions.

Atmospheric characterisation of HIP 67522 b with VLT/CRIRES+: VLT/CRIRES+ suggests a heavier planet and hints at deuterium fractionation

First Author: Lavail, A.
Instruments: CRIRES
ProgramIDs: 114.28HP
BibCode: 2026A&A...710A..85L

Context. Young transiting exoplanets provide unique opportunities to probe planetary atmospheres during critical early phases of evolution when atmospheric escape and contraction are most active. HIP 67522 b, a 17 Myr old hot Jupiter with an extraordinarily low bulk density (<0.20 g cm⁻³), represents an ideal target for high-resolution transmission spectroscopy. Aims. We aim to constrain the mass and characterise the atmospheric composition, thermal structure, and dynamics of HIP 67522 b using ground-based high-resolution near-infrared spectroscopy with VLT/CRIRES+, complementing recent JWST observations. Methods. We obtained 92 high-resolution spectra (R ≍ 10⁵) with VLT/CRIRES+ in the K2166 band during a transit on 30 January 2025. We applied cross-correlation techniques and Bayesian nested sampling retrievals to constrain molecular abundances, temperature structure, and atmospheric dynamics. Results. We detected H₂O at 20σ and CO at 5σ, confirming the extremely extended atmosphere of this low-mass giant. A velocity offset of −2.9 ± 0.2 km s⁻¹ indicates day-to-night winds. The rotation velocity has been constrained to <1.8 km s⁻¹ at 3σ, consistent with tidal locking. The retrieval analysis suggests a planetary mass of 27.7_−5.5^+5.9 Earth masses and statistically favours a two-temperature atmospheric structure with a discrete change at mbar pressures over an isothermal profile. This mass is twice as high as the mass estimated from JWST atmospheric observations and inconsistent at 3σ, casting doubt on the actual planetary density of the planet. No matter the choice of atmospheric model, we derived a supersolar C/O ratio that is about 1.5 times solar, along with a supersolar metallicity that might further increase if the atmosphere is cloudy, which is a degeneracy that our data alone cannot resolve. We report a tentative 2σ detection of HDO with an extreme enrichment factor of ∼1000 relative to the protosolar D/H ratio. If confirmed, this would be the first detection of deuterium in an exoplanet atmosphere and would require an intense escape rate to confirm its presence.

ExoplaNeT accRetion mOnitoring sPectroscopic surveY (ENTROPY): III. Optical He I line profiles of the accreting super Jupiter Delorme 1 (AB)b

First Author: Viswanath, Gayathri
Instruments: UVES
ProgramIDs: 110.23VU, 108.21ZE
BibCode: 2026A&A...710A..69V

Context. Observations of helium emission lines from classical T Tauri stars at high resolution (R_λ > 10 000) offer great potential, showing distinct profile characteristics that help probe regions within the accretion geometry untapped by hydrogen lines. Parallel studies in the planetary-mass regime have not been explored. Aims. We investigate helium line emission from the nearby (47 pc), wide orbit (∼84 au), ∼13 M_Jup, accreting circumbinary companion Delorme 1 (AB)b and analyse the resolved profile characteristics to infer clues to line origin. Methods. We obtained high signal-to-noise spectra of the target over 33 exposures with VLT/UVES over near-ultraviolet to optical wavelengths at high resolution (R_λ ~ 50 000). We studied the helium line profiles in the spectra and compared them to helium emission recorded from both accreting and non-accreting young stellar objects. Results. We detected seven neutral helium (He I) lines λλ3890, 4027, 4473, 4923, 5017, 5877, 6680 at high confidence (> 5σ), with notable flux variation between epochs. The line profiles of He I λλ5877,4923,4473,4027 show clear asymmetry, with a narrow component at ∼0 kms⁻¹ and a broad component redshifted by ∼15 kms⁻¹. The accretion luminosity (1.3_−0.7^+1.6 × 10⁻⁵ L_⊙) and mass accretion rate (0.7_−0.4^+0.9 × 10⁻⁸ M_Jup yr⁻¹) obtained from median He I line luminosities using empirical scaling relations from stars are comparable but slightly higher than from the target's ultraviolet excess emission. Conclusions. The protoplanet Delorme 1 (AB)b exhibits asymmetric He I lines similar to classical T Tauri stars, but with much smaller widths for the narrow and broad components. The triplet-singlet line ratio, a strong correlation with ultraviolet excess and the near-zero, redshifted velocities obtained for the narrow component suggest that it originates within the post-shock region, close to the planet surface. The persistent redshift of the broad component, its line width, and velocity correlation with the narrow component imply an origin within the shock structure, closer to the shock front. Emission seems to be dominated by accretion based on the obtained accretion luminosities, but a contribution from chromospheric activity may be present.

Stars on the ascending helium giant branch: I. From white dwarf merger to helium giant: the evolutionary state of the rapidly rotating hot subdwarf HE 1518-0948

First Author: Pritzkuleit, M.
Instruments: UVES
ProgramIDs: 71.D-0380, 167.D-0407
BibCode: 2026A&A...710A..99P

Hot subdwarf stars with masses above 0.8 M_⊙ ascend the helium giant branch after the end of core helium burning, before entering the white dwarf cooling track or exploding as type Ib/c supernovae. Such massive helium stars are typically expected to form through the stripping of an intermediate-mass star by a binary companion. Even after being stripped, the stars are expected to retain a detectable amount of hydrogen, but there is also the class of extreme helium-rich hot subdwarfs (He-sdOs), which show no traces, or only very weak traces, of hydrogen in their spectra. Several evolutionary channels have been proposed to explain their formation, but their extremely low binary fraction suggests that they are either created through single-star evolution triggered by a late hot flash in a low-mass red giant or the merger of two helium white dwarfs (WDs). Most He-sdOs are located close to the helium zero age main sequence, while a small number exhibit much lower surface gravities, indicating inflated radii. Whether these objects are evolutionarily connected to the main He-sdO population remains unclear. For this work we analysed the extreme helium-rich, low-surface-gravity sdO HE 1518─0948 (HE 1518) through a detailed spectroscopic study of optical and ultraviolet data. We measured an effective temperature of 52 000 ± 2500 K, a surface gravity log g of 4.64 ± 0.15 dex, an upper limit for the hydrogen abundance of log(n_He/n_H) < 2.5, and an exceptionally high projected rotational velocity of 90 ± 20 km s⁻¹, significantly higher than that of most known He-sdOs. The star is found to belong kinematically to the Galactic halo, consistent with the very low metallicity derived from our abundance analysis. A comparison with evolutionary models indicates that HE 1518 is the product of a massive double helium white dwarf merger and is currently undergoing helium shell burning while ascending the helium giant branch. This makes HE 1518 one of only a few known objects located in this sparsely populated region of the Hertzsprung─Russell diagram. Such stars provide valuable laboratories for studying the evolution of massive hot subdwarfs beyond core helium burning, and their high luminosities allow them to be detected at large distances.

Metal enrichment of galaxies in a massive node of the cosmic web at z ∼ 3

First Author: Wang, X.
Instruments: HAWKI
ProgramIDs: 110.23ZX
BibCode: 2026A&A...710A..65W

We present the mass-metallicity relation for star-forming galaxies in the protocluster MUSE Quasar Nebula 01 (MQN01) field, a massive cosmic-web node at z ∼ 3.245, hosting one of the highest overdensities of galaxies and active galactic nuclei found so far at z > 3. Through James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) spectra and images from JWST and Hubble Space Telescope (HST), we identified a sample of nine star-forming galaxies in the MQN01 field with a detection of nebular emission lines (Hβ, [OIII], Hα, [NII]), covering the mass range of 10^7.5 M_⊙ − 10^10.5 M_⊙. We present the relations of the emission line flux ratios versus stellar mass for the sample and derive the gas-phase metallicity (12 + log(O/H)) based on the strong-line diagnostics of [OIII]λ5008/Hβ and [NII]λ6585/Hα. Compared to the typical field galaxies at similar redshifts, MQN01 galaxies show relatively higher [NII]λ6585/Hα and lower [OIII]λ5008/Hβ at the same stellar mass, which implies a higher metallicity by about 0.26 ± 0.07 dex than on the field mass-metallicity relation. These differences decrease when we consider the fundamental metallicity relation, that is, when we also take the galaxy star formation rates into account. We argue that these results are consistent with a scenario in which galaxies in overdense regions assemble their stellar mass more efficiently (or, equivalently, start forming mass at earlier epochs) than field galaxies at similar redshifts.

Exploring the Central Region of SNR 0540-69.3 with JWST. I. Three-dimensional Morphology

First Author: Larsson, J.
Instruments: MUSE
ProgramIDs: 0102.D-0769
BibCode: 2026ApJ..1004....3L

The young supernova remnant SNR 0540-69.3 in the Large Magellanic Cloud offers a detailed view of an energetic pulsar-wind nebula (PWN) interacting with the surrounding ejecta. We present infrared observations of the central region of SNR 0540-69.3 obtained with the JWST NIRSpec and Medium-Resolution Spectrometer integral field units. From the observations we reconstruct the 3D morphology of the strongest emission lines in the inner ejecta (≲1000 km s⁻¹), which reveal the distributions of H I, He I, [Ne II], [Ne III], [S III], [S IV], [Fe II], and [Ni II]. The 3D morphology of most lines is dominated by two highly fragmented lobes of approximately similar size. Based on the assumption that the lobes are symmetric around the pulsar, we infer a pulsar kick velocity of ∼300 km s⁻¹ away from the observer. There are differences in the 3D morphologies of individual emission lines due to a combination of varying physical conditions and abundances. The detection of H I 1.8756 μm in the inner ejecta confirms the classification of the supernova as a Type II and shows that hydrogen was mixed down to low velocities of <400 km s⁻¹ in the explosion. We compare the results to the Crab Nebula and conclude that asymmetries originating in the explosion most likely play a major role in shaping these PWNe.

The atmosphere of the warm Neptune GJ 436 b probed with ESPRESSO

First Author: Herrero-Cisneros, E.
Instruments: ESPRESSO
ProgramIDs: 1102.C-0744
BibCode: 2026A&A...710A..82H

Aims. We aim to identify the presence of atomic and molecular species in the upper atmosphere of the warm Neptune-sized transiting planet GJ 436 b, which has a radiative equilibrium temperature of 690 K and a mass of 25.4 M_⊕. Methods. Using the transmission spectroscopy technique, we observed two full transits of GJ 436 b with the ESPRESSO spectrograph, covering the wavelength range from 3800 to 7880 Å. We searched for traces of atomic (H I, Li I, Na I, Mg I, V I, Cr I, Fe I, and Fe II), along with molecular (TiO, VO) species by directly detecting planetary absorption features and by cross-correlating the planetary spectrum with theoretical spectra computed for each investigated species. Results. Our analysis reveals no strong planetary detection for any of the species, consistent with a featureless optical spectrum. We derived upper limits by combining all ESPRESSO observations. Post-transit stellar flares were detected on both nights, primarily affecting chromospheric lines. A tentative Fe I signal appears in the first transit (S/N = 3.4 ± 0.2) at a wind velocity of ~−18.6 km s⁻¹, which is unexpectedly large for a cool planet. This weak signal is not present in the second transit and combined with its low significance, this suggests an origin in noise. In the less probable scenario where the feature is suppressed during the second transit by the higher stellar activity state, the T1 tentative signal peaks at 1300 K, which is above the equilibrium temperature of GJ 436 b. Ultimately, this result would imply a neutral iron abundance comparable to or exceeding that of the host star.

Nested, asymmetric H─He circumstellar shells in the Type Icn/Ibn SN 2024abvb

First Author: Anderson, J. P.
Instruments: FORS2, UVES, XSHOOTER
ProgramIDs: 114.2744
BibCode: 2026A&A...710A..35A

Context. Interacting transients probe mass loss in the final stages of stellar evolution; however, the geometry and timing of multi-episode mass loss remain poorly constrained. SN 2024abvb is a nearby interacting event with transitional Ibn/Icn spectroscopic properties and multi-epoch polarimetry, offering a rare opportunity to study structured circumstellar material (CSM). Aims. We aim to characterise the kinematics, composition, and geometry of the CSM around SN 2024abvb and to identify plausible progenitor and ejection scenarios that can produce the observed spectro-polarimetric evolution. Methods. We present high-resolution (VLT/UVES and VLT/X-Shooter) optical/NIR spectroscopy across several epochs, complemented by broadband polarimetry and spectropolarimetry (VLT/FORS2 and NOT/ALFOSC). Line identifications, velocity decompositions, and polarimetric time series were used to trace multiple kinematic components and changes in scattering geometry. Results. The high-resolution spectra reveal multiple narrow CSM components composed of He, C, and O with absorption minima at ∼150 − 400 km s⁻¹ and additional faster material up to ∼2000 km s⁻¹. Low-velocity Balmer absorptions are present, indicating distant H-rich material, a first in Type Ibn/Icn supernovae. Polarimetry shows a marked evolution (P ∼ 1% near the peak, ≲0.5% after ∼1 week, rising to ∼1.5% after ∼20 d with ∼50° position-angle rotation and to ∼4% after ∼30 d, stronger in the blue), implying a time-variable, wavelength-dependent scattering and obscuration component. The combination of kinematics and polarimetric behaviour is consistent with multiple, concentric toroidal shells with differing orientations and partial dust content.

The extremely low-luminosity Type Iax SNe 2022ywf and 2023zgx

First Author: Barna, B.
Instruments: EFOSC2
ProgramIDs: 112.25JQ, 108.220C
BibCode: 2026A&A...710A..72B

Context. We present the optical follow-up of SNe 2022ywf and 2023zgx, two examples from the Iax subclass of thermonuclear supernova (SN) events. With peak absolute magnitudes of M_V = −13.7 and −14.4 mag, respectively, both objects belong to the extremely low-luminosity (EL) population of the class. Aims. The common origin of SNe in the Iax subclass remains under debate, since the distribution of certain observables may indicate that the extremely low-luminosity explosions form a distinct population. We aim to estimate the physical properties of the two EL objects, including mapping the ejecta structure. We compare the results with the predictions of the pure deflagration model with similar luminosity, as well as with the common features of other SNe Iax. Methods. We performed spectral tomography on the spectral series of SNe 2022ywf and 2023zgx around their maxima to map the physical properties of the ejecta. Together with the analysis of BgVriz photometry, we studied a wide range of observables to investigate their distribution against luminosity. We compared the constrained chemical abundances of the ejecta to the predictions of hydrodynamic simulations with similar peak luminosities. Results. Constant abundances provide a good match for the distribution of chemical elements for both SNe 2022ywf and 2023zgx. The discrepancies compared to the least luminous pure deflagration model N5def_hybrid are minor, especially at post-maximum epochs. The two SNe also share similar characteristics in their constrained density structures, as well as in the evolution of the photosphere. Conclusions. The analysis supports the assumption that pure deflagration models can reproduce the main characteristics of SNe Iax, even for the low-luminosity population. The presented indirect observational evidence indicates that these objects show similar intrinsic properties to the well-studied, relatively luminous Iax sample and fit into the velocity distribution of the subclass.

Higher-resolution optical spectra of M_*< 10¹⁰ M_⊙ galaxies reveal outflow signatures unresolved by the SDSS

First Author: Hagedorn, B.
Instruments: EFOSC2
ProgramIDs: 113.269W
BibCode: 2026A&A...709A.242H

Galactic outflows are predicted to be ubiquitous in low-mass galaxies, but observational evidence is lacking. Both a low signal-to-noise ratio and a low spectral resolution can severely hamper the detection of galactic outflows, especially in small galaxies that have intrinsically narrow spectral lines. In an effort to overcome these issues, we obtained new, medium-high resolution (FWHM_inst ∼ 50 − 110 km/s) optical spectra of 52 local star-forming galaxies (0.01 < z < 0.03) with stellar masses 10^8.5 < M_*/[M_⊙]< 10¹⁰, using the TNG/DOLORES and NTT/EFOSC2 instruments. Our parent sample consists of galaxies from the Sloan Digital Sky Survey (SDSS) with available heterodyne single-dish molecular (i.e., CO) line data. The targets of this study are selected among those that, based on the comparison between CO line widths, SDSS spectral resolution, and corresponding SDSS-based Hα line widths, have a high chance of being unresolved by SDSS spectroscopy. Our new, medium-high resolution spectra reveal overall narrower Hα and [OIII]λ5007 lines, with signs of asymmetries and broad wings that are absent in the SDSS spectra of the same galaxies. This confirms our hypothesis that SDSS spectroscopy does not resolve the narrow emission lines of low-M_* galaxies, which hinders the detection of outflows. We identify outflow signatures in ∼30% of our targets based on the Hα line spectra. Assuming a typical bi-conical outflow geometry, this detection rate is consistent with theoretical predictions of ubiquitous outflows in the low-mass regime. The outflow incidence is enhanced (∼60%) for galaxies with above average star-formation rates (SFR) for the sample (SFR > 10^−0.74 M_⊙/yr). We estimate ionized gas mass outflow rates ranging from ∼0.1 − 50 × 10⁻³ M_⊙/yr (mean ∼20 × 10⁻³ M_⊙/yr) and corresponding mass loading factors between 0.03 and 0.14 (mean ∼0.07) for the sample.

The magnetic fields in Be stars are stronger than previously suggested

First Author: Hubrig, S.
Instruments: HARPS
ProgramIDs: 115.27WZ
BibCode: 2026A&A...710L...5H

Context. Recent observational studies suggest that Be stars most likely are formed through the process of mass transfer in binary systems. In view of the wide consensus that the origin of the magnetic field in stars with radiative envelopes involves binary interaction processes, searching for magnetic fields in Be stars appears especially promising. Aims. As a pilot project, we searched for the presence of magnetic fields in a sample of seven well-known Be stars. Methods. We used high-resolution HARPSpol spectra to measure the mean longitudinal magnetic field, employing the least squares deconvolution technique. A dedicated measurement procedure introduced by our group in recent years was applied. Results. Opposite to previous spectropolarimetric studies reporting that magnetic fields in Be stars are weak and usually below 100 G, our study presents the first observational evidence that magnetic fields in Be stars can be as strong as a few hundred gauss. Magnetic fields are detected in all studied Be stars, with the strongest magnetic field being about −460 G for the B0.5 III star HD 184915. Magnetic fields in the range between 338 and 380 G (in absolute values) are detected in three other Be stars, HD 209409, HD 209522, and HD 224686. Due to the fact that magnetic fields in Be stars are stronger than previously believed, we must re-evaluate our understanding of the initial conditions of massive binaries to be able to determine the origin of such systems.

VLTI-GRAVITY observations of blazars

First Author: Hovatta, Talvikki
Instruments: GRAVITY
ProgramIDs: 108.221C, 111.24L9, 112.25FL, 113.26E7
BibCode: 2026A&A...710A..15H

Aims. Parsec-scale jets of blazars have so far been spatially resolved only in millimeter and submillimeter wavelengths, where very long baseline interferometry can be used to obtain milliarcsecond-scale images of the jets. We have attempted to spatially resolve the near-infrared emission in jet-dominated blazars for the first time. Methods. We used the VLTI-GRAVITY instrument to obtain milliarcsecond-scale near-infrared interferometric observations of a flaring blazar Ton 599. Additionally, we observed four non-flaring blazars using the GRAVITY-wide mode, where a nearby bright star is used as a fringe tracker. Results. We modeled the squared visibilities of Ton 599 and found that they are incompatible with a single unresolved point source unless there is a significant amount of additional unknown coherence loss in the instrument. With the present data, we cannot distinguish between a model with an unresolved point source and extended emission or coherence loss and a model with a single Gaussian component. This suggests that we are seeing the unresolved or only partially resolved jet-base in near-infrared wavelengths. The wide-field mode of GRAVITY was challenging for the additional relatively faint targets, resulting in either non-detections or poor-quality data that could not be modeled. Conclusions. Our observations demonstrate that it is possible to detect the compact jet emission in blazars with near-infrared interferometry, suggesting that with the improved GRAVITY+ instrument it will be possible to spatially resolve and image the near-infrared emission of blazar jets.

Large Interstellar Polarisation Survey: III. Observational constraints on the structure of grains

First Author: Siebenmorgen, Ralf
Instruments: FORS2
ProgramIDs: 0102.C-0040
BibCode: 2026A&A...709A.277S

Our understanding of dust in the diffuse interstellar medium remains incomplete with regard to the structure, composition, size distribution, and alignment properties of its grains. Joint observations of reddening, starlight polarisation spectra, and polarised dust emission for individual sightlines provide essential constraints on such properties. We studied a far-UV-selected sample of 96 reddening curves, for which optical linear polarisation spectra were obtained with FORS at the VLT as part of the Large Interstellar Polarisation Survey. Starlight polarisation spectra for 60 stars are presented in this work. These data are combined with Gaia distance estimates and Planck thermal dust emission. A three-component dust model is made publicly available. It consists of nanoparticles, amorphous grains, and micrometre-sized dust agglomerates, with varying axial ratios, porosities, sizes, element abundances, and alignment efficiencies that match observations. The diversity of reddening and polarisation spectra is well reproduced by prolate grains with typical axial ratios of two, a porosity of 10%, and high alignment efficiencies. Such efficiencies can be achieved with radiative torque alignment theory but not with imperfect Davis-Greenstein alignment, except when adjusting the magnetic-field orientation to maximise the polarisation. Micrometre-sized dust contributes wavelength-independent grey extinction in the optical and accounts for about one-third of the visual extinction and one-third of the dust mass. A follow-up sub-millimetre survey with high-resolution polarimetry will further constrain grain shapes and alignment physics.

An Active Galactic Nucleus in the Antennae Galaxies?

First Author: Komugi, Shinya
Instruments: ALMA_Band_3
ProgramIDs: 2022.A.00032.S
BibCode: 2026ApJ..1004..126K

Time variability is a strong probe of energetic phenomena which occur at small spatial scales, like in active galactic nuclei (AGN). We use Atacama Large Millimeter/submillimeter Array observations at 100 GHz executed over a period of ∼2.5 months to look for time variability in the Antennae galaxies, a prototypical early stage merger galaxy pair, for which there are no previous signatures of an AGN in the optical, IR, or X-rays. Most 100 GHz detections of the Antennae are spatially extended and associated with star-forming regions, but two sources in the southern galaxy NGC 4039 are compact. One of these compact sources, S3, is offset by ∼1″ in the northeast direction from the stellar peak of NGC 4039, and marginally resolved at 10 pc resolution. The other source, S4, is cospatial with the stellar peak of NGC 4039 and unresolved even at a resolution of ∼4 pc. We examine the time variability of these two sources using their power spectra. We find that S4 varies with a characteristic timescale of 13 ± 3 days, indicating that the phenomenon responsible for the 100 GHz emission is smaller than 0.01 pc. By comparing the observed fluxes of the two sources with various candidate origins, we show that while S3 can be explained either by a young massive stellar cluster or an AGN, S4 is likely to be an AGN that is possibly Compton thick.

JWST's PEARLS: A Clumpy Ring Galaxy at z = 4.0148

First Author: Vizgan, David
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00035.L
BibCode: 2026ApJ..1004..114V

Ring galaxies are an uncommon class of galaxies whose morphology is closely related to dynamical processes that govern galaxy evolution. Some ring galaxies, known as "collisional ring galaxies," are thought to form as a consequence of head-on collisions between galaxies, and a number of high-redshift collisional ring galaxies have been discovered and/or studied in the era of the James Webb Space Telescope (JWST). In this paper, we present Hubble Space Telescope Advanced Camera for Surveys, JWST/NIRCam, and JWST/NIRSpec observations of a candidate ring galaxy at z_spec = 4.0148, previously identified as a potential gravitational lens. The galaxy exhibits a complex morphology, including three bright clumps along an apparent ring with radius ≍0 .″ 25 ≃ 1.8 kpc. It has a total star formation rate =140−30+20M⊙ yr⁻¹ and log(M*/M⊙)=10.41−0.13+0.11 , making it similar to other high-redshift collisional ring galaxies. Although we argue strongly in favor of the collisional ring explanation, we cannot entirely rule out a galaxy─galaxy strong lensing explanation for the system's morphology, in which a foreground galaxy at z ≃ 1.7 lenses a galaxy at z ≃ 4.0 into an Einstein ring-like configuration; to confirm the nature of this source, we require kinematic information via high spectral resolution observations. We suggest that current and future gravitational lens surveys should consider high-redshift ring galaxies as possible but significant contaminants.

Multiphase images of a powerful supernova-driven wind in the early Universe

First Author: Davies, Rebecca L.
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.00280.L, 2017.1.00428.L, 2011.0.00064.S, 2012.1.00523.S
BibCode: 2026MNRAS.549ag874D

Galactic winds are considered a likely driver of rapid quenching in early massive galaxies, but until now there has been no direct evidence that such systems drive winds powerful enough to meaningfully suppress their star formation. We present resolved cold gas and ionized gas observations of a powerful supernova-driven wind in a massive galaxy 1.1 billion years after the Big Bang (at z = 5.3). The outflow, likely triggered by ongoing merger activity, is removing gas at twice the rate of star formation and could plausibly eject all the cold gas from the galaxy within 100 Myr. Our results suggest that powerful merger-driven outflows may be a key mechanism to produce abundant massive quiescent galaxies in the early Universe when a large fraction of massive galaxies is interacting. The mass and energetics of this distant outflow are consistent with nearby starburst-driven superwinds, suggesting that the efficiency of stellar feedback has remained relatively constant over the last 12 billion years of cosmic history.

Direct detection of cool molecular gas in a star-forming galaxy at z=7.31

First Author: Cescon, Karin
Instruments: ALMA_Band_3
ProgramIDs: 2021.1.01495.S
BibCode: 2026MNRAS.549ag924C

We investigate the molecular gas content and interstellar medium (ISM) conditions of REBELS-25, a massive, star-forming galaxy at

$z=7.31$

. Deep VLA (Very Large Array) Q-band and Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 observations reveal CO(3−2) and CO(7−6) emission (both at

$\sim 3.5\sigma$

), and provide an upper limit on [C I](2−1). From the CMB (cosmic microwave background)-corrected CO(3−2) flux ─ representing the highest redshift detection of a low-J CO transition to date ─ we derive a molecular gas mass of

$M_{\rm mol} = (1.0\pm0.4)\times10^{11}\,(\alpha_{\rm CO}/(3\, \rm{M}_\odot(\rm{K\,km\,s^{-1}\,pc^{-2})^{-1}))\,M_\odot}$

, directly confirming the presence of a very massive gas reservoir only

$\simeq 700\,$

Myr after the big bang. This implies an extreme gas fraction of

$f_{\rm gas}\simeq 0.95$

, a gas-to-dust ratio of

$\delta _{\rm GDR}\simeq 6\times 10^2$

, and a depletion time-scale of

$\tau _{\rm dep}\simeq 1.2\,$

Gyr, broadly consistent with extrapolated scaling relations for main-sequence galaxies at lower redshift. Using the radiative transfer code TUNER, we self-consistently model CO and dust continuum emission in the context of the significant CMB background, constraining ISM properties and recovering

$M_{\rm mol}= (1.8^{+1.0}_{-0.9})\times 10^{11}\, \mathrm{M}_{\odot }$

, independent of assumptions about

$r_{31}$

and

$\alpha _{\rm CO}$

. We further discuss the use of alternative molecular gas tracers at early epochs. Combining CO and [C II] measurements, we infer an empirical [C II]-to-H

$_2$

conversion factor of

$\alpha _{\rm [C\, {\small II}]}=(60\pm 25)\,$

$\mathrm{M}_{\odot }$

$\mathrm{L}_{\odot }$

, suggesting [C II] remains a viable molecular gas tracer in the epoch of reionization. These results demonstrate the detectability of low-J CO emission even at

$z\gt 7$

, paving the way for next-generation facilities, and provide critical insights into the rapid mass assembly of galaxies during the first billion years of cosmic history.

Sub-kpc scale gas density histograms of the nearby barred spiral galaxy M83: multicomponent molecular gas structure reflecting the galactic environment

First Author: Matsusaka, Ren
Instruments: ALMA_Band_3
ProgramIDs: 2017.1.00079.S
BibCode: 2026MNRAS.549ag943M

We investigate the sub-kpc (sub-kiloparsec) molecular ISM (interstellar medium) structure and its relation to the galactic environment and star formation in the barred spiral galaxy M83 (NGC 5236). We employ the gas density histogram (GDH), which quantifies molecular gas surface density within

$550 \, \mathrm{pc}\times 550 \, \mathrm{pc}\times 100 \, \mathrm{km \, s^{-1}}$

cells. The GDHs are well described by one or two lognormal components, corresponding to the lower and higher surface-density molecular components, referred to as L-LN and H-LN, respectively. The L-LN mass (

$M_{\rm L}$

) is relatively uniform across the disc, whereas the H-LN mass (

$M_{\rm H}$

) is highly structured and traces spiral arms. The fractional contribution of the H-LN component (

$f^{\prime }_{\rm H}$

) shows coherent structures across the disc and is enhanced along spiral arms, consistent with our previous Milky Way results. Moreover, while the L-LN correlates only weakly with star formation rate surface density (

$\Sigma _{\rm SFR}$

) and shows a steep Kennicutt─Schmidt (KS) relation with surface-density saturation reminiscent of atomic gas, the H-LN exhibits a tighter, nearly linear correlation similar to the conventional molecular KS relation. These results provide direct evidence that the molecular gas in M83 consists of multiple components. Star formation is more closely linked to the H-LN component, whereas the L-LN component appears to represent a more spatially extended molecular gas. Overall, our results suggest that galactic environments control the relative contribution of the two LN components, and that enhanced H-LN contribution is associated with elevated star formation activity.

A nine-member protostellar system forming via filament fragmentation in the high mass protocluster NGC 6334-43

First Author: Taylor, D. J.
Instruments: ALMA_Band_6
ProgramIDs: 2019.1.00246.S, 2017.1.00180.S
BibCode: 2026MNRAS.549ag922T

We present the serendipitous discovery of a nine-member system comprised of protostellar and candidate prestellar sources in

$\sim$

350 au-resolution images from Complex Chemistry in hot Cores with ALMA (CoCCoA). The system is bound in a stability analysis, has a mean separation between pairs of 7930 au, and appears to have formed via the fragmentation of a single large-scale filamentary structure traced by 1.20 mm continuum and H

$^{13}$

$^+$

J = 3─2 emission. Two multiples within the nine-member system, a triple and a binary, have properties consistent with formation by core fragmentation on

$\sim$

1500─1700 au scales. The hot core NGC 6334-43 is resolved into two components (ALMA2a/ALMA2b) separated by 618 au and driving a bipolar outflow traced by

$^{12}$

CO J = 2─1 and SiO J = 5─4 in

$\sim$

1250 au-resolution archival Atacama Large Millimeter/submillimeter Array (ALMA) data. Only one other source in the nine-member system is clearly protostellar: ALMA6a, which drives an outflow traced by

$^{12}$

CO. The outflow properties of ALMA2a/ALMA2b and ALMA6a are consistent with high-mass and low-mass Class 0 sources, respectively. By fitting the CH

$_{3}$

CN J = 13─12 emission towards ALMA2a, ALMA2b, and ALMA6a, we derive M

$_{\rm vir}$

= 4.5, 5.4, and 2.6 M

$_{\odot }$

, respectively. The other six sources in the nine-member multiple have M

$_{\rm gas}$

= 0.50─1.87 M

$_{\odot }$

and appear young, as indicated by their sparse mm-wavelength line emission and non-detection in published cm continuum observations. Our results highlight the potential of serendipitous discoveries in ALMA surveys to add to the small observational sample of young high-mass protomultiple systems.

Observations of highly inclined disks with ALMA: Results from ¹²CO gas and continuum observations

First Author: Martinien, L.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2018.1.00958.S, 2016.1.00460.S, 2022.1.00742.S, 2016.1.00771.S, 2013.1.01175.S, 2016.1.01505.S
BibCode: 2026A&A...710A.140M

Aims. We aim to study the radial and vertical extents of ¹²CO gas, millimeter (mm) dust thermal emission and optical/near-infrared scattered light by dust in highly inclined protoplanetary disks. These parameters are indicators of radial drift and vertical settling, and essential to setting better constraints on planet formation. Additionally, we aim to provide estimates of the dynamical stellar masses, including cases where no such prior measurements exist. Methods. We analyzed a sample of 14 highly inclined protoplanetary disks for which the vertical extent of the emission layers could be constrained directly. We presented ALMA high-angular-resolution band 7 (0.9 mm) continuum images and ¹²CO (3-2) gas moment maps, as well as HST and VLT/SPHERE scattered light images. We estimated the dynamical masses using position-velocity diagrams. Results. The majority of disks in our sample (11 out of 14) follow R_gas > R_{dust, μm} > R_{dust, mm}, while the other 3 disks (including 2 residing in multiple systems) appear to be more extended in the mm continuum than in scattered light. Highly inclined disks tend to appear less radially extended in CO gas line emission than in the mm dust continuum, compared to less inclined disks. This results from optical depth effects and/or radial drift. The known correlation between disk size and the mm continuum and line fluxes have been confirmed on the basis of our sample, with highly inclined disks shown to be significantly fainter than disks seen at a lower inclination for a given disk radius. We found that this correlation is significantly tightened once fluxes have been corrected for the disk inclination. This is consistent with the disks being optically thick at mm wavelengths. Regarding the vertical extent defined as the apparent emitting height, most disks in our sample follow H_gas > H_{dust, mm}. This strengthens our previous findings, which state that the mm dust is highly decoupled from the gas and forms a layer in the disk midplane that is attributed to vertical settling. Most disks appear more vertically extended in gas than in scattered light, suggesting that the micron-sized (μm-sized) dust is not fully coupled to the gas. We also estimated the dynamical masses, for the first time, for the majority of the objects in our sample. We found an anticorrelation between the dynamical mass and the aspect ratio, emphasizing the dominant role of gravity in setting the disk vertical extent. However, we found no correlation with the disk radius.

Compact CO emission and no evidence of radial drift: ALMA observations of the faintest planet-forming disks in Lupus

First Author: Ricciardi, G.
Instruments: ALMA_Band_7
ProgramIDs: 2023.1.00428.S
BibCode: 2026A&A...710A.112R

Context. A large fraction of the planet-forming disks surveyed by ALMA show faint CO emission, which is commonly interpreted as an indication of severe CO depletion. However, disks can be faint for multiple reasons, including by having their emission unresolved spatially, which may result in their size being overestimated, making their flux appear faint. The limited sensitivity of previous observations prevented us from determining whether this scenario can indeed account for the observed faint CO emission for radially compact disks, hindering our understanding of disk evolution and planet formation in most of the disk population. Aims. We present new ALMA observations targeting ¹²CO (J = 3─2) and ¹³CO (J = 3─2) in 17 of the faintest planet-forming disks in Lupus. We aim to test the feasibility of the compact disk scenario as a plausible explanation for compact disks with faint CO isotopolog emission. Methods. Our sample contains 17 disks observed with ALMA in Band 7 at the moderate angular resolution of 0_⋅^''25 (≍20 au radius at 160 pc, the median distance of the sample), approximately one order of magnitude deeper than the available archival ALMA data where ¹²CO and ¹³CO were not detected. We used line stacking techniques to enhance the signal-to-noise ratio and extract the CO fluxes when possible. Finally, we compared the CO line luminosities with a grid of physical-chemical models of extended and compact disks and computed the disk dust and CO sizes. Results. We detected ¹²CO and ¹³CO emission in ten disks. Four disks were detected only in ¹²CO, and three disks were not detected in either of the two isotopologs. Conclusions. The observations indicate that some of these disks are consistent with being intrinsically compact and optically thick, in both ¹²CO and ¹³CO. This scenario offers an alternative explanation to the commonly accepted hypothesis of significant CO depletion. The derived gas radii further support this interpretation (R_CO ≤ 40 au), suggesting that a significant fraction of disks may be born intrinsically small, as is also indicated by recent Class 0/I surveys. Furthermore, the resulting gas-to-dust size ratios reveal no clear signs of dust evolution, suggesting that these compact disks are not drift-dominated.

Resolving circumgalactic gas flows around a z ≍ 3.6 quasar using MUSE and ALMA

First Author: Galbiati, M.
Instruments: ALMA_Band_3, MUSE, UVES
ProgramIDs: 094.A-0131, 096.A-0222, 109.232M, 092.A-0011, 65.O-0296, 2024.1.00499.S, DataDoiProID
BibCode: 2026A&A...710A.117G

The formation and evolution of galaxies is regulated by the exchange of gas with the surrounding large-scale structures on circum- and intergalactic scales, yet little is known about the complex processes shaping the cycle of baryons in and out of galaxies. In this work, we present a multiline study of the gas surrounding a z ≍ 3.66 quasar known to host one of the brightest Lyα nebulae at high redshift, MUSE Quasar Nebula 04 (MQN04). By combining a high-resolution MUSE detection of nonresonant He II emission with a precise measurement of the redshift of the quasar host via the ALMA CO(4─3) line, we study the kinematics of the cool ionized gas down to #x2248; 1 kpc from the quasar. The MUSE observations reveal complex clumpy structures as well as diffuse emission extended over ≍100 kpc and blueshifted by ≍0 − 800 km s⁻¹ relative to the quasar systemic redshift, suggesting that the circumgalactic medium is highly asymmetric. The analysis of the He II/Lyα line ratio, and the presence of a low-column density (≍ 10^14.6 cm⁻²) H I absorber along the quasar sightline suggests that MQN04 resides in a highly ionized medium. This is also supported by the gas kinematics, which, except in the most central region, shows consistent velocity shifts across the different tracers, indicative of relatively weak radiative transfer effects. Based on its morphology and kinematics, we conclude that the extended He II emission may arise from merger-driven tidal stripping or inflows of gas illuminated by the quasar radiation. On comoving megaparsec scales, we discover a large concentration (δ ≍ 41) of star-forming galaxies lying within |∆v_QSO| ≲ 1000 km s⁻¹ from the quasar. MQN04 is therefore one of the most overdense environments discovered at this epoch.

The Qz5 Survey. II. Metallicity Evolution of Damped Lyα Systems Out to z ∼ 5

First Author: Wisz, M. E.
Instruments: XSHOOTER
ProgramIDs: 098.A-0111, 0100.A-0243
BibCode: 2026ApJ..1003..222W

Damped Lyα absorbers (DLAs) are the highest H I column density (N_{H I}) absorption line systems detected in the spectra of background quasars. DLAs dominate the neutral gas content of the Universe (Ω_HI) and are used to measure the metallicity evolution of H I gas. In this work, we introduce a sample of five recently detected DLAs at z > 4.7, found in mid- to high-resolution spectroscopy from VLT/X-shooter and Keck/HIRES. These DLAs were not preselected based on metallicity, enabling an unbiased study of the metallicity of H I gas at z ∼ 5. We also search for DLAs unbiased in metallicity at 0 < z < 5.5 from the literature, we apply a combined correction for dust depletion and α-enhancement (assuming no depletion of S, Si, and Zn) to Fe abundances, and we measure the cosmic metallicity evolution of α-elements using a linear fit with a slope of −0.22 ± 0.05 dex per unit redshift. For the highest redshift bin, we find an N_{H I} weighted average of = −2.00. This value is 4.4σ deviant from the trend recovered at z < 4.7 and a K-S test comparison gives a 2.4σ difference. We conclude that the metallicity of H I gas sharply decreases at z ∼ 5, in agreement with previous tentative evidence. This sharp decrease may be connected with the onset of the enrichment of galaxies' circumgalactic media or with the end of cosmic reionization; though, we cannot exclude that it is driven by small sample statistics.

Multiwavelength Study of Blue Straggler Stars in Tombaugh 2: Evidence for Binary Mass Transfer and Constraints on Cluster Dynamical State

First Author: Bisht, D.
Instruments: FLAMES, GIRAFFE
ProgramIDs: 076.D-0220
BibCode: 2026ApJ..1003..182B

We present a focused multiwavelength study of blue straggler stars (BSSs) in the intermediate-age open cluster Tombaugh 2, located in the outer Galactic disk, to constrain the dominant formation pathways of BSSs in a low-density environment. Cluster members are identified using Gaia DR3 astrometry through a Gaussian mixture model, yielding a clean sample of high-probability members. Color─magnitude diagram analysis indicates an age of ∼1.74 Gyr. The radial surface density profile is well described by a King model, indicating a centrally concentrated overall structure, while the cluster exhibits only weak or no clear evidence of mass segregation among its stellar populations. We identify 26 BSS candidates and two yellow straggler star candidates. Spectral energy distributions constructed from ultraviolet, optical, and infrared photometry reveal that nine BSSs (∼32%) exhibit significant ultraviolet excess, indicating an additional hot component. Binary spectral energy distribution decomposition identifies stripped companions with effective temperatures T_eff ≍ (1.5─8) × 10⁴ K and radii R ≍ 0.04─0.28 R_⊙, consistent with proto─white dwarfs, extremely low-mass pre─helium white dwarfs, and young hot remnants formed through recent mass transfer. A slight central concentration of BSSs, together with stripped companions, suggests that binary mass transfer is an important formation channel, with no evidence for merger-driven formation. Multiepoch Very Large Telescope/FLAMES spectroscopy reveals radial velocity variability in several systems, providing independent evidence for binarity. Our results highlight that optical─infrared photometric analyses alone may fail to detect hot compact companions, while spectroscopy and ultraviolet observations provide complementary constraints, with ultraviolet data offering a direct probe of such companion s in intermediate-age open clusters.

JWST Exoplanetary Worlds and Elemental Survey (JEWELS). II. Condensation Temperature Trends and Galactic Chemical Evolution in JWST Planet-hosting Stars

First Author: Sun, Qinghui
Instruments: ESPRESSO, FEROS, HARPS, UVES
ProgramIDs: 089.C-0471, 1102.C-0744, 090.C-0146, 1102.C-0249, 097.C-0280, 192.C-0852, 099.C-0431, 0103.C-0360, 60.A-9122, 60.A-9036, 0102.D-0185, 089.D-0202, 108.22JQ, 109.23FU, 110.246L, 112.25HY, 112.25T4, 106.21ER
BibCode: 2026ApJS..284...57S

We present high-precision chemical abundances for 25 FGK-type stars hosting exoplanets observed in JWST Cycle 3 programs and all Guaranteed Time Observations and Director's Discretionary Time programs from Cycles 1─3, based on high-resolution, high-signal-to-noise ratio optical spectra from ground-based telescopes. Using a strictly differential, line-by-line analysis relative to the Sun, we derive homogeneous stellar parameters and abundances for 19 elements with an atomic number Z ≤ 30. The sample spans a wide range of stellar properties, with [Fe/H] = −0.6 to +0.4 dex and effective temperatures between 4700 and 6600 K, and includes hosts of terrestrial and giant planets as well as multiplanet systems. We refine carbon and sulfur abundances in cool dwarfs using a spectral synthesis, mitigating systematics from line blending. Several chemically interesting systems are identified, including mildly α-enhanced metal-poor stars and multiplanet hosts with elevated [C/O]. Using isochrone ages, we derive empirical Galactic chemical evolution (GCE) relations and examine condensation temperature (T_cond) trends before and after a GCE correction. The T_cond slopes show no dependence on stellar or planetary properties, indicating that they reflect a mixture of multiple mechanisms, with planet-related signatures entangled in GCE and stellar evolution effects. Thus, T_cond trends require careful interpretation. Several systems with significantly positive or negative T_cond slopes are identified. Together with forthcoming JWST atmospheric measurements, this homogeneous stellar abundance catalog provides a basis for probing star─planet chemical connections and planet formation pathways.

Cloudy with a chance of metals: Indications of CO₂ in the atmosphere of GJ 1214 b from high-resolution K-band spectroscopy

First Author: Nortmann, L.
Instruments: CRIRES
ProgramIDs: 108.22CH, 108.22PH, 109.23HN, 111.254J, 113.26GE
BibCode: 2026A&A...710A..29N

Context. Sub-Neptune extra-solar planets are abundant in the Milky Way, yet their atmospheric properties remain poorly understood. They frequently exhibit muted transmission spectra, with GJ1214b being the most prominent example. Following years of intense observing campaigns yielding featureless planetary spectra, more recent observations with JWST have revealed the first possible atmospheric signatures of H₂O, CH₄, and CO₂. Aims. We present high-resolution transmission spectroscopy of GJ 1214 b based on eight transits obtained with the CRIRES⁺ spectrograph in the K band. Methods. We used SYSREM to remove telluric and stellar signals from the data and searched for signatures of H₂O, CO, CH₄, H₂S, NH₃, and CO₂ using the cross-correlation technique. Results. We obtained non-detections for the first five molecules and used injection recovery tests to derive upper limits on the atmosphere. For CO₂ we measure a cross-correlation signal at S/N ~3.6, with a detailed investigation of the signal showing no obvious indication that it is caused by correlated noise. A Welch t-test confirmed that the in-trail, in-transit distribution is significantly different from the out-of-trail distribution at a 3.4σ confidence. Interpreting the data using a Bayesian retrieval framework, with multiple molecular species and free chemistry, resulted in a retrieved planet temperature of T_iso = 398₋₁₉₇⁺²⁸³ K, consistent with a value intermediate between the day- and night-side temperatures from JWST-derived temperature-pressure profiles at high altitudes, as expected for the planetary terminator. In addition, a metallicity of [M/H]= 0.48_−1.70^+0.89 was derived from the abundances of the retrieved molecules, along with an opacity deck pressure of log₁₀(P_c) = −3.04_−1.53^+2.52. A simpler equilibrium chemistry retrieval assuming CO₂ as the sole opacity source returned a compatible temperature, with smaller formal uncertainties (T_iso = 509₋₅₉⁺¹⁰² K), slightly higher metallicity ([M/H]= 1.51_−0.75^+0.68), and higher opacity deck pressure (log₁₀(P_c) = −0.88_−2.48^+1.95). While these sets of values correspond to relatively large signal amplitudes predicted for CO₂ features in the mid-infrared, they are compatible with JWST NIRSpec observations within the models' 1.5σ uncertainties. Conclusions. Further modelling and additional data are required to confirm the atmospheric signatures and obtain a comprehensive interpretation of low- and high-resolution data. Overall, our results support previous findings that CO₂ is likely to be a significant component of the atmosphere of GJ 1214 b.

Planet-forming disks and their environment across regions and time from the full NIR census

First Author: Garufi, A.
Instruments: SPHERE
ProgramIDs: 111.24XN, 0101.C-0383, 0103.C-0470, 1100.C-0481, 1104.C-0415, 099.C-0891
BibCode: 2026A&A...709A.269G

The evolution of planet-forming disks and the processes of planet formation influence each other, and both of them are possibly impacted by the local environment. Extensive high-resolution imagery of disks across space and time is the best tool for determining their evolution. We compiled a comprehensive list of disk-bearing young stars with near-IR high-contrast images available. The sample sums up to 268 sources, including 51 targets with no prior publications, which makes this study the largest of its kind and the most extensive release of IR disk images to date. Our census reveals very diverse disk and ambient morphologies. Disks in Lupus are bright, in Chamaeleon they are faint, in Corona Australis and Taurus they are frequently surrounded by ambient emission. Disks experience an abrupt increase in IR brightness between 2 Myr and 5 Myr. The earliest IR disk cavities around single stars arise after 2─3 Myr, which explains why young disks are faint in the near-IR and determines which disks can live longer. Well-known, high-longevity disks (>8 Myr) are always bright. Ambient material is detected in more than 20% of young sources but the fraction drops with time. We find clear correspondence for the presence of ambient material with the stellar variability, near-IR excess, and mass accretion rate as well as, in turn, with spirals and shadows in disks. Half of the disks with ambient material show spirals while none of them show rings. We therefore propose that the spirals and the disk warps responsible for shadows are generally induced by late infall from the medium, and that this also affects stellar accretion. The emerging picture proves the fundamental role of the environment for disk evolution and planet formation.

Towards a Measurement of the Primordial Helium Isotope Ratio

First Author: Cooke, Ryan J.
Instruments: CRIRES, UVES
ProgramIDs: 081.D-0854, 091.C-0851, 194.C-0833, 107.22U1, 110.23QS, 112.25D8
BibCode: 2026ApJ..1003..225C

We report the discovery of two metastable neutral helium (He I*) absorbers in the Milky Way, and use the upgraded CRyogenic InfraRed Echelle Spectrograph (or CRIRES) on the Very Large Telescope to determine the helium isotope ratio, ³He/⁴He, along these sight lines. We have also obtained deeper observations of a third sight line to report a ≲4% precision measure of ³He/⁴He in the Orion Nebula. These data have allowed us to place a 2σ limit on the time variability of He I* absorption in the Orion Nebula, dlog10[N(HeI∗)/cm−2]/dt≤7.2×10−4dexyr−1 (<0.17% yr⁻¹), suggesting that these absorbers are in radiative equilibrium. We compute new galactic chemical evolution models of the Milky Way, and use our observations to infer the primordial helium isotope ratio and a scaling factor for the yields reported by nucleosynthesis calculations. Based on the data and models that we report here, we infer a best-fit value (³He/⁴He) P=(1.15−0.21+0.24)×10−4 , which agrees with Big Bang nucleosynthesis calculations that assume the Standard Model of particle physics in combination with the baryon density inferred from cosmic microwave background temperature fluctuations. We infer the stellar yield scale relative to the solar metallicity, y/Z⊙=2.12−0.29+0.31 , which is somewhat higher than previously found. Finally, we note that the forthcoming generation of extremely large telescopes is poised to determine ³He/⁴He in more metal-poor environments, enabling a model-independent determination of the primordial value. *Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme(s) 081.D-0854(B), 091.C-0851(A), 107.22U1.001, 110.23QS.001, 110.23QS.002, 112.25D8.001, 112.25D8.002, 194.C-0833(A), and 194.C-0833(D).

The Bulge Cluster Origin (BulCO) survey with CRIRES at the ESO-VLT: A chemical screening of the globular cluster NGC 6553

First Author: Bartolomei, A.
Instruments: CRIRES
ProgramIDs: 110.24A4
BibCode: 2026A&A...710A..48B

In this paper, we present the chemical screening of the stellar population belonging to the globular cluster NGC 6553 in the Galactic bulge. This study has been conducted in the contest of the Bulge Cluster Origin (BulCO) survey, an ESO-VLT Large Program that is currently ongoing with CRIRES in the near-infrared (NIR) domain. This survey is performing an unprecedented chemical screening of 17 stellar systems orbiting the Milky Way bulge, with the aim of unveiling their origin and true nature. Here we present and discuss the abundances of 18 elements produced via distinct nucleosynthetic channels for 14 red giant branch stars belonging to NGC 6553. We found a mean [Fe/H] = −0.20 ± 0.01 deX, and about solar-scaled iron-peak elements, confirming that this is one of the most metal-rich globular clusters in the Milky Way. We also found [X/Fe] enhancement of α and several other light elements. Furthermore, we assessed the presence of multiple populations typical of genuine globular clusters from the significant spreads in Na, N, and C, along with an almost vertical Na-O anticorrelation. Finally, by using classical ([α/Fe] versus [Fe/H]) and newly-defined ([V/Fe] and [Zn/Fe] versus [Fe/H]) "chemical DNA tests", we have proven its in situ formation within the Galactic bulge.

Seeing through the dust: Unraveling near-infrared variability in type 2 active galactic nuclei

First Author: Ceron-Meneses, J.
Instruments: VIRCAM
ProgramIDs: 179.A-2005, 198.A-2003, 1104.A-0643, 110.25A2, 284.A-5026
BibCode: 2026A&A...709A.245C

Context. Near-infrared (NIR) variability studies of active galactic nuclei (AGNs) are still limited, as long-term multiepoch monitoring in the NIR is observationally challenging. The depth, wavelength coverage, and 14-year temporal baseline of UltraVISTA make it one of the few surveys capable of providing a detailed characterization of AGN variability in this regime. Aims. We aim to quantify the NIR variability of known AGNs in the COSMOS field and to investigate the physical origin of variability in type 2 AGNs. In particular, we examine how NIR variability can help clarify the discrepancies between optical and X-ray classifications. Methods. Using the 14-year multiepoch UltraVISTA DR6 dataset in the YJHK_s bands, we constructed calibrated NIR light curves and quantified their variability through a set of metrics. Active galactic nucleus-like stochastic variability was identified by modeling the light curves with a damped random walk (DRW) process. Results. We find that ∼7─17% of the 533 type 2 AGNs are variable in the NIR, with variability fractions increasing toward K_s, where the dusty torus dominates the emission. Based on the wavelength dependence of the DRW variability amplitude, we classify variable type 2 AGNs into disk-dominated, torus-dominated, and highly obscured groups. About one third of the X-ray unobscured (XR I) type 2 AGNs are variable in the NIR, consistent with misclassified weak type 1 or "true type 2" AGNs. On the other hand, 21.4% (30/140) of the X-ray obscured (XR II) type 2 AGNs show detectable variability in the NIR, most of them only in H or K_s, consistent with obscuration of the bluer (accretion disk) bands. Type 2 AGNs without X-ray counterparts (165) show the smallest fraction (3.6%) of variable objects. Conclusions. NIR variability provides an effective and independent diagnostic for confirming optical classifications and for identifying weak or misclassified type 1 AGNs in deep extragalactic surveys.

Hourly radio variability of PDS 70c from time-differential photometry

First Author: Casassus, Simon
Instruments: ALMA_Band_7
ProgramIDs: 2017.A.00006.S, 2018.A.00030.S, 2022.1.01477.S
BibCode: 2026A&A...710L..10C

Context. The radio emission mechanisms from accreting protoplanets and their variability link observations and physical properties. Aims. We revisit the variability of the ∼343 GHz (ALMA Band 7) flux density from PDS 70c (F_B7). Methods. The subtraction of the extended time-averaged signal may enable the measurement of the flux density from variable and embedded point sources. Visibility alignment and self-calibration yield close to thermal residuals in each execution block (EB) of ALMA observations, thus allowing the time-differential photometry of point-sources in the visibility domain. The variability of PDS 70c was checked against synthetic control point sources. Results. In images of the 2017 ALMA dataset, with three ∼1 h EBs, PDS 70c was detected only on 6 December 2017, where F_B7 rose by 228%±69% (3.3σ). Time-differential photometry confirms a rise by 170%±46% (3.7σ). An application to ∼2 h EBs from the 2023 dataset resulted in constant flux densities, within a scatter of ∼15%. However, F_B7(t) shows some scatter when splitting the deep 2023 EBs into 20 min intervals, with a χ² test significant at 2.6σ, and an intrinsic dispersion of 49%±21%. Conclusions. The radio variability of PDS 70c, observed over hours but averaged out on longer timescales, is indeed expected if the signal is due to H I free-free from an accretion shock on a circumplanetary disk surface. A planet-to-environment mass ratio < 10⁻⁴ is required to avoid smoothing by radiative diffusion if the signal is due to thermal emission from the environment.

The ALPINE─CRISTAL─JWST Survey: The Fast Metal Enrichment of Massive Galaxies at z ∼ 5

First Author: Faisst, Andreas L.
Instruments: ALMA_Band_7
ProgramIDs: 2021.1.00280.L, 2017.1.00428.L, 2019.1.00226.S, 2022.1.01118.S
BibCode: 2026ApJ..1004...22F

We present the stellar mass─metallicity relation (MZR) and mass─metallicity─star formation relation ("fundamental metallicity relation"; FMR) of 18 massive ( log(M⋆/M⊙)=9.5−11 ) main-sequence galaxies at z ∼ 5 from the ALPINE─CRISTAL─JWST sample. This sample complements recent studies by JWST at up to 2 orders of magnitude lower stellar masses. The metallicities are derived using strong optical lines and verified by temperature-based oxygen abundance measurements for five galaxies for which faint auroral lines are detected. We find that the metal abundance evolves, on average, from 40% to 60% solar between z ∼ 5 and cosmic noon (z ∼ 2) at the massive end of the MZR, suggesting already significant metal enrichment at early times. The FMR at z = 5 exhibits a 5× larger scatter (preferentially to lower metallicities) compared to the local FMR relation. This scatter can be explained by a bursty star formation and the direct buildup of metals in early galaxies, as well as differences in age and outflow efficiencies. Capitalizing on all available samples, we find that the observed MZR and FMR over 3 orders of stellar mass is generally in good agreement with results from cosmological simulations, although some underestimate the metal enrichment at low stellar masses. This may be due to too efficient metal-rich outflows. We show that the ALPINE─CRISTAL─JWST galaxies likely joined the current FMR at z ∼ 10 and will evolve into massive ( log(M⋆/M⊙)∼11.4 ) galaxies with supersolar metallicities by z = 0.

MUSE-DARK: III. The evolution of the radial acceleration relation at intermediate redshifts

First Author: Ciocan, B. I.
Instruments: MUSE
ProgramIDs: 094.A-0289, 095.A-0010, 096.A-0045, 1101.A-0127
BibCode: 2026A&A...709L..16C

Context. The radial acceleration relation (RAR) is a tight empirical correlation between the observed radial acceleration (a_tot) and the baryonic radial acceleration (a_bar) measured across galaxy radii; these two accelerations start to deviate significantly from each other below a characteristic acceleration scale, a₀. To date, observational studies of the RAR have predominantly focused on galaxies in the local Universe, leaving its evolution with cosmic time largely unexplored. Aims. Using high signal-to-noise data from the MUSE Hubble Ultra Deep Field survey, we investigated the RAR with a sample of 79 star-forming galaxies (complete above M_★ > 10^8.8 M_⊙) at intermediate redshifts (0.33 < z < 1.44). Methods. We estimated the observed intrinsic acceleration (a_tot) and the baryonic acceleration (a_bar) from a disk-halo decomposition that incorporates stellar, gas, and dark matter components, with corrections for pressure support, using 3D forward modelling. Results. We find a RAR in our intermediate-z sample offset from the local relation, with a higher characteristic acceleration scale ( a₀|_z∼1 = 2.38^+0.12_−0.10 × 10⁻¹⁰ m/s² a 0 | z ∼ 1 = 2 . 38 − 0.10 + 0.12 × 10 − 10 m / s 2 ) and a larger intrinsic scatter (∼0.17 dex). Dividing the sample into redshift bins and refitting the RAR in each bin, we find a characteristic acceleration scale that systematically increases with z. Parametrising the z-dependence as a₀(z) = a₀(0)+a₁ ⋅ z, we obtain a₁ = 1.59^+0.11_−0.10 × 10⁻¹⁰ m/s² a 1 = 1 . 59 − 0.10 + 0.11 × 10 − 10 m / s 2 , providing evidence for a z-evolution. We find similar results using various dark matter halo profiles as well as the modified Newtonian dynamics framework in our 3D forward modelling. Conclusions. Our results show that the RAR persists at intermediate redshifts, with statistically significant redshift evolution of the characteristic acceleration, pointing to a possible evolution of the baryon-missing mass connection over cosmic time.

Dust activity of interstellar comet 3I/ATLAS (C/2025 N1) at 4.3─4.5 au from VLT/FORS2 imaging

First Author: Pratik, Prajwal
Instruments: FORS2
ProgramIDs: 115.29F2
BibCode: 2026MNRAS.549ag867P

We present R-band coma characterization of interstellar comet 3I/ATLAS (C/2025 N1) from archival VLT/FORS2 imaging spanning 2025 July 4─21 at

$r_h = 4.35$

─4.53 au ─ the earliest VLT/FORS2 morphological dataset for this object. After Moffat PSF fitting to remove field stars, aperture photometry yields

$Af\rho = 110$

─458 cm (

$\rho = 2{_{.}^{\prime\prime}} 5$

$\sim$

7000 km) across four reliable epochs, consistent with independent contemporaneous measurements. Radial surface-brightness slopes

$\gamma = -2.6$

$-5.0$

are far steeper than the canonical

$\gamma = -1$

, implying radiation-pressure sweeping, grain fragmentation, or time-variable emission at these distances. The coma is nearly circular (

$e \lesssim 0.07$

) within

$\rho \lt 5$

arcsec (

$\sim$

14 000 km), with no position-angle alignment to the antisolar direction. A systematic jet search using Larson─Sekanina filtering and azimuthal-median subtraction yields no coherent features; injection-recovery tests confirm 90 per cent completeness for jets with

$\gtrsim 8$

per cent peak contrast at

$\rho = 5{_{.}^{\prime\prime}} 0$

. Since a wobbling jet was detected from August 3 onward, our non-detection through July 18 constrains the emergence of this feature to a 16-d window (July 18─August 3,

$r_h \approx 4.5 \rightarrow 4.0$

au), consistent with thermally activated onset. Dust activity at

$r_h \gt 4.3$

au requires a driver more volatile than H

$_2$

O, consistent with the CO

$_2$

-dominated coma confirmed by James Webb Space Telescope (JWST) spectroscopy.

Nitrogen enrichment through stellar chemical feedback at parsec scale in NGC 5253 as seen with MUSE─NFM

First Author: Pruijt, Brigitte G. A.
Instruments: MUSE
ProgramIDs: 095.B-0321, 1104.A-0026
BibCode: 2026MNRAS.549ag794P

NGC 5253 is a nearby (D = 3.6 Mpc) Blue Compact Dwarf galaxy, notable for its three massive young super star clusters (SSCs) and nitrogen enrichment. Its similarity to extreme star-forming galaxies at high redshift makes it a good local analogue for studying chemical enrichment at high spatial resolution. We characterize the ionized gas and dust in the giant H II region in the proximity of the three SSCs in the centre of NGC 5253 using new Multi-Unit Spectroscopic Explorer Narrow Field Mode adaptive optics-assisted data at unprecedented spatial resolution of 0

${_{.}^{\prime\prime}}$

15 (

$\sim$

2.3 pc). We derive the attenuation for the central SSCs and, for the first time, map the extinction parameter (

$R_V$

) in an extragalactic object.

$R_V$

varies among SSCs, suggesting differences in dust physics. Electron temperature and density diagnostics yield flat temperature distributions

$T_\mathrm{e,median}$

([N II])

$=12000 \pm 1700$

K and

$T_\mathrm{e,median}$

([S III])

$= 11\,000 \pm 600$

K, and a structured

$n_e$

([S II]) of maximum

$1930 \pm 40$

$^{-3}$

. The direct method gives a flat helium abundance (

$10^3y^+ = 81 \pm 4$

) and uniform oxygen abundance (

$12 + \log (\text{O/H}) = 8.22 \pm 0.05$

). N/O shows a factor 2─3 enhancement around the SSCs, mapped here for the first time at such high spatial resolution. The total excess nitrogen mass is

$\sim$

0.3

$\mathrm{ M}_\odot$

, which we estimate is producible by the observed WN-type Wolf─Rayet (WR) stars. Since there is no direct spatial overlap between the enrichment and WR star positions, the N-rich material appears to have been expelled from the original sites.

Joint X-Ray, Kinetic Sunyaev─Zeldovich, and Weak Lensing Measurements: Toward a Consensus Picture of Efficient Gas Expulsion from Groups and Clusters

First Author: Siegel, Jared C.
Instruments: OMEGACAM, VIRCAM
ProgramIDs: 179.A-2004, 177.A-3017, 177.A-3018, 177.A-3016
BibCode: 2026ApJ..1003..151S

There is no consensus on how baryon feedback shapes the underlying matter distribution from either simulations or observations. We confront the uncertain landscape by jointly analyzing new measurements of the gas distribution around groups and clusters—DESI+ACT kinetic Sunyaev─Zel'dovich (kSZ) effect profiles and eROSITA X-ray gas masses—with mean halo masses characterized by galaxy─galaxy lensing. Across a wide range of halo masses (M₅₀₀ = 10¹³⁻¹⁴M_⊙) and redshifts (0 < z < 1), we find evidence of more efficient gas expulsion beyond several R₅₀₀ than predicted by most state-of-the-art simulations. A like-with-like comparison reveals all kSZ and X-ray observations are inconsistent with the fiducial 1 Gpc³ hydrodynamical FLAMINGO simulation, which was calibrated to reproduce pre-eROSITA X-ray gas fractions: eROSITA X-ray gas fractions are 2 × lower than the simulation, and the kSZ measurements are combined >8σ discrepant. The FLAMINGO simulation variant with the most gas expulsion, and therefore the most suppression of the matter power spectrum relative to a dark-matter-only simulation, provides a good description of how much gas is expelled and how far it extends; the enhanced gas depletion is achieved by more powerful but less frequent AGN outbursts. Joint kSZ, X-ray, and lensing measurements form a consistent picture of gas expulsion beyond several R₅₀₀, implying a more suppressed matter power spectrum than predicted by most recent simulations. Complementary observables (e.g., thermal Sunyaev─Zel'dovich effect and fast radio bursts) and next-generation simulations are critical to understanding the physical mechanism behind this extreme gas expulsion and mapping its impact on the large-scale matter distribution.

MUSE Analysis of Gas around Galaxies (MAGG): VII. Emission line galaxies near strong blended Lyα absorption systems at z ≳ 3

First Author: Galbiati, Marta
Instruments: MUSE, UVES, XSHOOTER
ProgramIDs: 189.A-0424, 109.2314, 166.A-0106, 097.A-0089, 094.A-0585, 099.A-0159, 094.A-0280, 094.A-0131, 092.A-0011, 093.A-0575, 091.A-0833, 077.A-0166, 083.A-0042, 073.B-0787, 074.A-0306, 69.A-0613, 073.A-0071, 073.A-0653, 68.A-0461, 68.A-0492, 68.A-0600, 71.A-0114, 68.B-0115, 65.O-0299, 67.A-0022, 197.A-0384, 71.A-0067, 080.A-0482, 096.A-0937, 095.A-0200, 075.A-0464
BibCode: 2026A&A...709A.233G

We investigate the connection between strong, blended Lyα absorption systems (SBLAs) and ≍1000 Lyα-emitting galaxies (LAEs) at z ≳ 3 in 28 quasar fields from the MUSE Analysis of Gas around Galaxies (MAGG) survey. Selecting SBLAs as spectral regions with transmitted flux −0.05 < F < 0.25 over ≍ 138 km s⁻¹ bins, we find a strong correlation with LAEs within a projected distance of R ≤ 300 kpc and line-of-sight velocity separation of |∆v| ≤ 300 km s⁻¹. The association rate increases significantly with decreasing flux, a trend that persists also at smaller separations (R < 100 kpc). A two-dimensional cross-correlation analysis confirms significant clustering of LAEs around SBLAs, while no such clustering is seen for spectral regions with F > 0.25. The correlation appears to also depend on the width of the spectral window used to identify SBLAs, with a larger window yielding a stronger signal. Our analysis confirms that SBLAs serve as probes of the circumgalactic medium (CGM) at the interface between the Lyα forest and the optically thick Lyman limit systems. The significant dependence of the LAE-SBLA cross-correlation on the spectral binning used to select these absorbers motivates future tests of the current SBLA framework as a tracer of halos.

ALMAGAL: VIII. Early phases of triggered star formation in source AG286.0716─1.8229

First Author: Mininni, C.
Instruments: ALMA_Band_4, ALMA_Band_6
ProgramIDs: 2023.1.01386.S, 2019.1.00195.L
BibCode: 2026A&A...709A.173M

Context. Several theoretical and observational studies have shown that new waves of triggered star formation can be induced by the feedback from newly formed massive protostars, due to the expansion of H II regions. Aims. We used the millimeter dust continuum data of the ALMAGAL survey and the Anderson et al. (2014) catalog of H II regions to search for signatures of possible triggered star formation at its onset, and selected one ALMAGAL source for ALMA follow-up observations. Methods. For this study we selected the source AG286.0716─1.8229, in which six cores were detected at a resolution of ~7600 au, but only two at a higher resolution. The four cores not detected at higher resolution are prestellar core candidates. We used archival data from the SARAO Meerkat Galactic Plane Survey and Rapid Askap Continuum Survey to confirm whether a H II region is present in the field. We observed the source with ALMA in Band 4, covering the emission of DCO⁺(2─1), N₂D⁺(2─1), DCN (2─1), and CH₃CCH (9─8), to infer from the chemical composition and temperature estimates whether these cores are in an early phase of the star-formation process, which allows us to classify them as prestellar cores. The new Band 4 continuum image revealed additional three cores outside of the ALMAGAL field of view (FoV), making a total of nine cores in the region, eight of which are located along an arch that has a radius of ~0.75 pc. We also used the continuum and molecular emission to estimate the mass of these cores, to determine whether they are gravitationally bound or transient objects. Results. We have derived a spectral index between −0.14 and −0.4, in the frequency range of 0.8─1.6 GHz for the candidateH II region, which is consistent with optically thin free-free emission. The H II region spatially coincides (as projected on the plane of the sky) with the position of one of the cores, which in the new ALMA Band 4 observations does not have a compact morphology. The N₂D⁺and DCO⁺emission peaks at the position of three out of four prestellar core candidates, and the overall emission in both the line and the continuum, which extends outside of the FoV of the ALMAGAL observations, reveals a clear arched shape centered on the H II region. We were able to estimate the gas temperature of only the most evolved core, using the CH₃CCH emission. The resulting value of 39 ± 5 K is also an upper limit for the other cores. Using plausible temperature ranges for each core, based on the information from chemical tracers and the dust continuum, we derived mass ranges for the cores (~2─16 M_⊙) as well as ranges for the virial parameter (~0.3─5). All the cores along the arch have virial parameters consistent with bound objects, with only one exception. Conclusions. Comparing the typical separation and mass of the cores with those expected in the case of the collect and collapse scenario and with the thermal Jean length and mass, the best agreement is found with the characteristic scales in the case of triggered star formation. The same methodology can be applied to further ALMAGAL sources to identify optimal targets to study a larger sample of prestellar cores in an environment affected by the presence of a H II region.

The Keplerian Disk, Envelope, and Streamers Surrounding an Early O-type Protostar in the Sagittarius C Cloud of the Central Molecular Zone

First Author: Weng, Jixiang
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00641.S
BibCode: 2026ApJ..1003..219W

Disk-mediated accretion is central to theories of massive star formation, setting the initial conditions for their evolution. Yet observations of Keplerian disks around early O-type protostars remain scarce, as they are often blended into complex surrounding structures. We report Atacama Large Millimeter/submillimeter Array Band 6 observations (300 au resolution) of an accretion disk surrounding a high-mass protostar in the Sagittarius C cloud in the Central Molecular Zone (CMZ) around the Galactic center. We identify spectral lines and analyze the spatial distribution of the emission of the complex organic molecules. We use a dynamical model with an inner Keplerian disk and an outer free-fall envelope to fit the three-dimensional position─position─velocity data of the stacked CH₃OCHO molecular lines and constrain the mass of the central protostar to be ∼40−3+2M⊙ . The fitting results additionally show that the disk has a centrifugal radius at about 1300 au. Considering the infall velocity, radius, and mass of the envelope, we estimate the accretion rate from the envelope onto the disk to be ∼7 × 10⁻³ M_⊙ yr⁻¹. We also identify spiral-like structures in the disk that can be described by free-falling streamers. Our results highlight the critical role of accretion disks and streamers in the mass accumulation of early O-type stars in the CMZ.

Digging into the Massive Protostar S255IR NIRS3: A Study of Nitrogen-bearing Molecules and Their Prebiotic Chemistry

First Author: Manna, Arijit
Instruments: ALMA_Band_4
ProgramIDs: 2016.A.00008.T
BibCode: 2026AJ....171..368M

The study of complex nitrogen-bearing molecules is essential for probing the physical and chemical evolution of star-forming regions. In this paper we present the identification of rotational emission lines from several complex N-bearing species such as methyl cyanide (CH₃CN), ethyl cyanide (C₂H₅CN), vinyl cyanide (C₂H₃CN), cyanamide (NH₂CN), and formamide (NH₂CHO) toward the high-mass protostar S255IR NIRS3 using Atacama Large Millimeter/submillimeter Array band 4 observations. In addition, the vibrationally excited transitions of cyanoacetylene (HC₃N, ν₇ = 2) were detected. The column densities and excitation temperatures of these molecules were derived through LTE spectral modeling, yielding excitation temperatures in the range of 175─220 K. The high excitation temperatures (175─220 K) indicate that the identified N-bearing molecules arise from the warm inner regions (T ≥ 100 K) of the source. The fractional abundances were further estimated relative to H₂, CH₃OH, and CH₃CN. A Pearson correlation heat map of the abundances reveals a strong positive correlation (r > 0.7) among three molecules in the cyanide family, such as CH₃CN, C₂H₃CN, and C₂H₅CN, suggesting that these N-bearing molecules may be chemically linked. Comparison with three-phase warm-up chemical models shows that the observed abundances of CH₃CN, C₂H₅CN, C₂H₃CN, NH₂CN, NH₂CHO, and HC₃N (ν₇ = 2) relative to H₂ are consistent with model predictions within factors of 1.04, 0.67, 1.28, 0.76, 0.72, and 0.96, respectively. Finally, we discuss the potential formation pathways of the identified N-bearing molecules in the context of gas-grain chemistry within S255IR NIRS3.

ATOMIUM: inner circumstellar envelopes of oxygen-rich AGB stars as revealed by highly excited SiO lines

First Author: Pimpanuwat, B.
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00659.L
BibCode: 2026MNRAS.549ag888P

Silicon monoxide (SiO) traces the physical conditions and dynamics in the circumstellar envelopes (CSEs) of asymptotic giant branch (AGB) stars. We present high-resolution ALMA Band 6 observations of highly excited SiO emission in 14 oxygen-rich AGB stars. We cover transitions from

$\upsilon =0$

to 8, including first detections of

$^{28}$

SiO

$\upsilon =3,4,8$

$J=6-5$

$^{29}$

SiO

$\upsilon =6$

$J=6-5$

, and

$^{30}$

SiO

$\upsilon =4,5$

$J=6-5$

, some of which are masers. The

$\upsilon =8$

transition is the highest

$\upsilon$

-state observed in an AGB star yet. Masers in

$\upsilon =0$

are detected clearly in V PsA and IRC+10011 and tentatively in T Mic. R Hya exhibits the richest SiO spectrum. SiO

$J=6-5$

absorption is seen in R Aql, R Hya, S Pav, and T Mic, with features indicative of both infalls and outflows, and tentative detection of

$^{28}$

SiO

$\upsilon =8$

$J=6-5$

absorption is found towards S Pav and R Aql. Highly excited SiO emission is often distributed in arcs or clumps with velocity gradients; components in R Hya and U Her align with predicted shock fronts. Detection rates show no significant difference between low and high mass-loss rate stars, although line overlap may affect some intensities. Maser detections appear uncorrelated with pulsation period or phase. The radius enclosing 90 per cent of compact SiO emission shows a tentative correlation with mass-loss rate. These results highlight the role of mass loss and CSE geometry in shaping high-excitation SiO emission.

Reading between the Rings: Observed Dust Ring Properties as Probes of Planet Masses

First Author: Faruqi, Amena
Instruments: ALMA_Band_7
ProgramIDs: 2018.A.00030.S
BibCode: 2026ApJ..1003..215F

We hypothesize that dust rings in protoplanetary disks formed by an embedded planet should have properties that reflect the planet's mass. We use 2D hydrodynamical simulations of planet─disk interactions to investigate this, focusing on planets ranging from 0.5─2.0× the pebble-isolation mass, for three different aspect ratios. We find the ring's dust mass, peak location, and width to correlate with planet mass. We confirm a positive linear relationship between a planet's Hill radius and the location of a ring's density peak and demonstrate how this relationship can be used to constrain planet masses in observed systems by applying it to PDS 70. The dust ring width and mass change with planet mass for planet masses up to the pebble-isolation mass, beyond which they become constant. The steepness of the gas pressure radial profile is asymmetric, with the direction of the asymmetry being determined by whether the planet mass is above or below the pebble-isolation mass. We therefore propose a new way to define the pebble-isolation mass: the minimum planet mass that perturbs the gas enough for the pressure gradient interior to the pressure maximum to exceed the pressure gradient exterior to it. We discuss how our findings could be used to constrain or estimate planet masses from gas or dust observations of disks with measurable substructures and apply our results to five disks in the exoALMA sample to estimate planet masses and constrain disk aspect ratios. We also discuss how the potential for planetesimal formation in a ring varies with planet mass.

An almost NIRCam-dark dusty star-forming galaxy at z = 6.63

First Author: Bing, Longji
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_7
ProgramIDs: 2019.1.01722.S, 2013.1.00884.S
BibCode: 2026MNRAS.549ag846B

We present AC-2168, an almost NIRCam-dark, millimetre-bright galaxy. The source was identified blindly in Atacama Large Millimeter/submillimeter Array (ALMA) Band-4 continuum data and remains undetected in the COSMOS-Web DR1 NIRCam catalogue. We spectroscopically confirm a redshift of

$z_{\rm spec}=6.631$

from [

${\rm C\, {\small II}}$

] 158

$\mu$

m and four tentatively detected CO lines in the data from the NOrthern Extended Millimeter Array (NOEMA) and ALMA. Modelling to near-IR to millimetre photometry yields

$L_{\rm IR}=1.6^{+0.6}_{-0.4}\times 10^{12}\, \mathrm{L}_\odot$

${\rm SFR}=244^{+82}_{-55}\, \mathrm{M}_\odot \, \rm yr^{-1}$

$M_\star =3.7^{+12.2}_{-2.6}\times 10^{10}\, \mathrm{M}_\odot$

, and

$A_{\rm V}=5.4\pm 1.6$

mag. From the millimetre continuum and [

${\rm C\, {\small II}}$

] emission, we infer a warm interstellar medium with

$T_{\rm dust}=60\pm 11K$

$M_{\rm dust}=3.0^{+0.8}_{-0.5}\times 10^{8}\, \mathrm{M}_\odot$

, and

$M_{\rm gas}=4.1\pm 0.8\times 10^{10}\, \mathrm{M}_\odot$

. AC-2168 differs from normal UV-selected galaxies in its strong dust obscuration, yet its moderate star formation rate (SFR) at high

$M_\star$

, consistent with the star-forming main sequence, distinguishes it from most blindly detected dusty star-forming galaxies dominated by intense starbursts. Its short depletion time of

$\sim 170\, \rm Myr$

, compact (

$\sim 1\, \rm kpc$

) dust-continuum size, and moderate SFR suggest a massive system caught in a rapid transition near the end of its main assembly phase, consistent with NIRSpec-based star formation histories of massive quiescent galaxies at

$z\sim 4-5$

. We also estimate a space density of

$\rm 7.8^{+18.0}_{-6.5}\times 10^{-6}\, cMpc^{-3}$

for AC-2168-like NIRCam-dark galaxies at

$z\sim 6-7$

, which reaches

$\sim 42\hbox{ per cent}$

of the abundance of massive quiescent galaxies at

$z\sim 4-5$

. These results jointly suggest that NIRCam-dark galaxies are likely the direct progenitors of a substantial fraction of massive quiescent galaxies.

A Multiscale Molecular and Atomic Gas View on the H II Region N113 in the Large Magellanic Cloud: Evidence for High-mass Star Formation Triggered by Supersonically Colliding H I Flows

First Author: Yamada, Rin I.
Instruments: ALMA_Band_6, PI230
ProgramIDs: 0103.F-9315, 0103.F-9515, 2015.1.01388.S
BibCode: 2026ApJ..1003...68Y

The Large Magellanic Cloud (LMC) exhibits vigorous high-mass star formation, including the H II regions of 30 Dor, which is the most active site of star formation in the Local Group. This paper focuses on the Giant Molecular Cloud (GMC) in the H II region N113 in the central part of the LMC. Based on the ¹²CO(J = 2─1) and ¹³CO(J = 2─1) data at a resolution of ~0.2 pc obtained by the Atacama Millimeter/submillimeter Array and the Atacama Pathfinder Experiment, we reveal that the GMC consists of two filamentary structures, each ~10 pc in length, forming a V-shaped pattern with a vertex angle of 90°. The filamentary structures host high-mass young stellar objects in gravitationally bound dense gas. Large-scale H I gas data covering 100 pc reveal two distinct velocity components separated by more than 40 km s⁻¹that correspond to the low-velocity (L-) and disk (D-) H I components of the LMC. The L-component appears to be located in a cavity-like distribution of the D-component, and the CO filaments are positioned at the cavity's edge. We find evidence for the L-component to fit the cavity by a 53 pc displacement, and suggest that collisional compression of the H I gas during the last 1.3 Myr triggered the GMC formation and the high-mass star formation. This lends support to the idea that the large-scale collision driven by the tidal interaction is playing a role in the evolution of the interstellar medium in N113.

The RoPES project with HARPS and HARPS-N: III. Two candidate planets orbiting the G-type star HD 161098

First Author: Nari, N.
Instruments: ESPRESSO, HARPS
ProgramIDs: 113.26U2, 115.28BD, 109.2392, 112.25SF, 105.20PH, 192.C-0852, 198.C-0836, 091.C-0936, 183.C-0972, 072.C-0488
BibCode: 2026A&A...709A.123N

Context. The development of refined instruments and techniques for a detailed analysis of the radial velocities (RVs) of stars other than the Sun allows the presence of planetary signals of amplitude below 1 m s⁻¹ to be investigated. Long-term RV surveys allow the detection of Earth-like and super-Earth-like planets in the habitable zones of Sun-like stars, prime targets for future missions for the atmospheric characterization of exoplanets. Aims. We present the analysis of the nearby G8 V-type star HD 161098 (V = 7.68 mag, d = 29.75 pc). We searched for terrestrial planets in the habitable zone. Methods. We combined historical datasets with new data collected in an ongoing blind search program with HARPS, HARPS-N, and ESPRESSO. We utilized recently developed tools to extract RVs and to deal with the analysis of stellar activity. We performed a joint analysis of RVs and activity indicators to separate the planetary signals from those related to activity. Results. We detected two sub-m s⁻¹ signals that we claim as candidate planets. We are not able to confirm their nature with certainty. Candidate HD 161098 b has an orbital period of 72.578_−0.060^+0.059 d and a minimum mass of 3.63 ± 0.59 M_⊕. HD 161098 c has an orbital period of 682.5_−9.9^+9.5 d and a minimum mass of 7.8_−1.4^+1.5 M_⊕. If confirmed, candidate HD 161098 c would reside in the optimistic habitable zone of the star. We find a magnetic cycle of 4090₋₁₃₀⁺¹⁴⁰ d period and a rotation period of 28.22_−0.35^+0.30 d. Our analysis sets the stage for future observing campaigns of the star, finalized for the confirmation of our results. Conclusions. We are entering the sub-m s⁻¹ era at long orbital periods with a combination of stellar activity treatment and long-term campaigns.

The ESO SupJup Survey: X. A carbon isotope contrast in the young ROXs 12 system

First Author: Grasser, N.
Instruments: CRIRES
ProgramIDs: 110.23RW
BibCode: 2026A&A...709A.141G

Context. Emerging research suggests that elemental and isotopic ratios of exoplanet and brown dwarf atmospheres may serve as potential tracers of their formation pathways. The ESO SupJup Survey aims to shed light on this hypothesis, with a focus on the ¹²CO/¹³CO ratio, by investigating the atmospheric composition of substellar companions and isolated brown dwarfs. Aims. In this work, we aim to characterize the atmospheres and determine the ratios of ¹²CO/¹³CO of the Rho Ophiuchus X-ray source (ROXs) 12 system (∼6 Myr), consisting of an M0 host with an L0 companion, as part of the ESO SupJup survey. This system provides a great opportunity to directly compare the atmospheric compositions of the host star and its companion. Methods. Using high-resolution CRIRES+ K band spectra of these objects, we perform atmospheric retrieval analyses to derive their atmospheric properties, including the ¹²CO/¹³CO ratio. Our retrieval framework is built on the radiative transfer code petitRADTRANS, with which we generate model spectra based on equilibrium chemistry tables computed with FastChem, coupled with the nested sampling algorithm PyMultiNest. Results. We report the presence of H₂O, ¹²CO, ¹³CO, and HF in both the star and companion, with a tentative detection of H¹⁸₂O in ROXs 12B. The ¹²CO/¹³CO ratios of the two objects show a measurable, though not strongly significant, difference, namely 77₋₇⁺¹⁰ and 55₋₇⁺¹⁰ for ROXs 12A and B. Both are consistent with the local present interstellar medium. We measure a C/O ratio of 0.54 ± 0.01 and obtain a lower limit of H¹⁶₂O/H¹⁸₂O ⪆ 300 for ROXs 12B, while the C/O ratio of the star is not reliably constrained due to the absence of atomic oxygen lines in the K band. The companion also appears to exhibit a more isothermal temperature structure than expected from models. Furthermore, we retrieve moderate veiling in the host star of r_k = 0.17_−0.03^+0.02. Conclusions. Systems such as ROXs 12, in which both star and planet can be chemically and isotopically characterized, are crucial for constraining potential formation mechanisms of massive, wide-orbit super-Jupiters. The differing ¹²CO/¹³CO ratios in the ROXs 12 system highlight the need for a broader sample to assess the frequency of isotopic variations and whether they may be linked to formation history.

Two hot pre-white dwarfs inside the red giant branch planetary nebula Pa 13: Double-core evolution or common-envelope-induced rejuvenation

First Author: Reindl, Nicole
Instruments: XSHOOTER
ProgramIDs: 109.22YV, 111.24MQ
BibCode: 2026A&A...709A.112R

The close binary central stars of planetary nebulae (PNe) offer a unique window for investigating the conditions that immediately follow the ejection of a common envelope (CE). Double-eclipsing and double-lined double systems are particularly valuable as they provide minimally model-dependent constraints on fundamental binary parameters. In this context, we report that the nucleus of Pa 13 (P = 0.3988 d) belongs to this rare class of systems and we present a comprehensive analysis of its double-degenerate binary. We performed a two-component nonlocal thermodynamic equilibrium spectral analysis based on phase-resolved X-shooter spectroscopy, multiband light-curve modeling, spectral energy distribution fitting, and a kinematic analysis. Both stars are found to be hot pre-white dwarfs, with Star 1 being cooler but larger (T_eff = 50.0 kK, R = 0.40 R_⊙) than Star 2 (T_eff = 75.0 kK, R = 0.16 R_⊙). The weakness of the spectral lines of Star 2 made both the atmospheric and radial velocity (RV) analyses challenging, and we uncovered a strong sensitivity of the assumed surface ratio to its derived RV curve. However, the RV curve and Kiel mass of Star 1 (M₁ = 0.41 ± 0.02 M_⊙) could be determined precisely, which allowed for a dynamical mass determination of Star 2 (M₂ = 0.39 ± 0.04 M_⊙). Moreover, we uncovered that Pa 13 exhibits a small but significant orbital eccentricity (e = 0.02 ± 0.01), which makes it only the second post-CE binary central star with a measured eccentricity. Our kinematic analysis shows that Pa 13 belongs to the Galactic halo, implying a system age of ≍11 Gyr. We conclude that Pa 13 provides the strongest evidence so far that PNe can be observed around post-red giant branch stars. Immediately after the CE ejection, Star 1 likely still filled its Roche lobe, which suggests that Pa 13 is a more evolved, detached descendant of over-contact double-degenerate systems such as Hen 2-428. Since the mass ratio of Pa 13 is close to unity, the system may have formed through double-core CE evolution. Alternatively, there must exist an efficient CE-induced rejuvenation mechanism capable of reheating the cool white dwarf in the binary, as already indicated by the Hen 2-428 system.

MIGHTEE-H I: the star-forming properties of H I-selected galaxies

First Author: Tudorache, Madalina N.
Instruments: VIRCAM
ProgramIDs: 179.A-2006, 179.A-2005
BibCode: 2026MNRAS.548ag810T

The interplay between atomic gas and the star formation history (SFH) of a galaxy are intrinsically linked, and we need to decouple these dependencies to understand their role in galaxy formation and evolution. In this paper, we analyse the SFH of 203 galaxies from the MIGHTEE-H I Survey Early Science Release data, cross-matched to with multiwavelength photometry across the COSMOS and XMM-LSS fields. We focus on the relationships between H I properties and star formation, with a sample which primarily traces gas-rich, star-forming systems at low redshift, extending to low stellar masses and probing regimes that are difficult to access with optically selected samples. A strong correlation emerges between a galaxy's H I-to-stellar mass ratio and the time of formation, alongside an inverse correlation between stellar mass and time of formation, regardless of the inferred SFH. Additionally, galaxies with lower stellar masses and higher H I-to-stellar mass ratios exhibit longer gas depletion times compared to more massive galaxies, which appear to have depleted their gas and formed stars more efficiently. This suggests that smaller, gas-rich galaxies have higher depletion times due to shallower potential wells and less efficient star formation. Within this H I-selected sample, the efficiency of star formation is regulated primarily by stellar mass and gas fraction, with low-mass galaxies retaining extended atomic reservoirs due to inefficient conversion of H I into stars.

Fundamental effective temperature measurements for eclipsing binary stars ─ VIII. NIRPS spectroscopy of CD−27 2812

First Author: Adshead, N. J.
Instruments: HARPS, NIRPS
ProgramIDs: 112.25UD
BibCode: 2026MNRAS.548ag723A

There are very few M-dwarfs with accurate independent measurements of their mass, radius, and effective temperature (T

$_{\rm eff}$

) that can be used to test stellar models for these low-mass stars. We aim to use high-resolution near-infrared spectroscopy to measure the mass of M-dwarfs in eclipsing binary systems with solar-type stars and to measure the flux ratio between the two stars at near-infrared wavelengths. This information can then be combined with the analysis of the light curve, photometry, and the parallax to measure the mass, radius, and T

$_{\rm eff}$

for both stars. We have used the TESS light curve and spectra observed with the HARPS and NIRPS spectrographs to measure the following model-independent radii and masses for CD─27 2812, an F9 V star in an eclipsing binary with a much fainter M-dwarf companion on a short near-circular orbit (P=7.8 d):

$R_1 = 1.721 \pm 0.004 R_{\odot }$

$R_2 = 0.531 \pm 0.002 R_{\odot }$

$M_1 = 1.3597 \pm 0.0024 {\rm M}_{\odot }$

, and

$M_2 = 0.5624 \pm 0.0006 {\rm M}_{\odot }$

We show how the NIRPS spectra can be used to measure the flux ratio in the J and H bands. This information, combined with published photometry and the Gaia DR3 parallax, leads to the following effective temperature measurements:

$T_{\rm eff,1} = 6197 \pm 55$

$T_{\rm eff,2} = 3770 \pm 28$

K. This study demonstrates that it is now feasible to use eclipsing binaries to accurately measure T

$_{\rm eff}$

for M-dwarf stars for which we also have independent mass and radius measurements.

High CO/H₂ ratio supports an exocometary origin for a CO-rich debris disc

First Author: Smith, K. D.
Instruments: CRIRES
ProgramIDs: 111.255A, 110.248L
BibCode: 2026A&A...709A..76S

Context. Over 20 exocometary belts host detectable circumstellar gas, mostly in the form of CO. Two competing theories for its origin have emerged, positing that the gas is either primordial or secondary. Primordial gas survives from the belt's parent protoplanetary disc and is therefore H₂-rich. Secondary gas is outgassed in situ by exocomets and is relatively H₂-poor. Discriminating between these scenarios has not been possible for belts that host unexpectedly large quantities of CO. Aims. We aim to break this gas origin dichotomy through direct measurement of H₂ column densities in two edge-on, CO-rich exocometary belts around ∼15 Myr-old A-type stars, constraining the CO/H₂COH2 ratio and CO gas lifetimes. Observing edge-on belts enables rovibrational absorption spectroscopy against the stellar background. Methods. We present near-IR CRIRES+ spectra of HD 110058 and HD 131488, which provide the first direct probe of H₂ gas in CO-rich exocometary belts. We targeted the H₂ (v=1-0 S(0)) line at 2223.3 nm and the ¹²CO v = 2 → 0 rovibrational lines in the range 2333.8-2335.5 nm and derived constraints on column densities along the line of sight to the stars. Results. We detect ¹²CO strongly, but not H₂, in the CRIRES+ spectra. This allows us to place 3σ lower limits on the CO/H₂COH2 ratios of >1.35 × 10⁻³ and >3.09 × 10⁻⁵ for HD 110058 and HD 131488, respectively. These constraints demonstrate that, at least for HD 110058, the exocometary gas is compositionally distinct and significantly H₂-poor compared to the <10⁻⁴ CO/H₂<10−4COH2 ratios typical of protoplanetary discs. For HD 131488, we further compared the CO photodissociation timescale to the age of the system through simple shielding arguments, and find that we cannot formally rule out a primordial origin; however, we suggest that a more realistic model of CO survival likely supports a secondary origin for this system as well. Overall, a high CO/H₂COH2 ratio for HD 110058 indicates that the gas in this CO-rich belt is most likely not primordial in composition, supporting the presence of exocometary gas.

Deciphering the Explosion Mechanism of Type Ia Supernovae Using Their Remnants. II. A Deep Dive into Double Detonations with SNR 0509-67.5

First Author: Mandal, Soham
Instruments: MUSE
ProgramIDs: 0104.D-0104
BibCode: 2026ApJ..1002..155M

Type Ia supernovae (SNe) occur when a white dwarf (WD) explodes via runaway thermonuclear burning. To date, major uncertainties remain regarding the nature of the explosion mechanism and its observable signatures. In this work, we study how the double-detonation explosion mechanism, or helium shell detonation in a sub-Chandrasekhar WD followed by core detonation, shapes SN remnants (SNRs) and encodes information about the WD progenitor. We evolve a suite of double-detonation SN models to the remnant phase, up to several centuries after the explosion, and measure the characteristic sizes of substructures formed in the SNR due to turbulent mixing. By comparing our models to high-resolution optical observations of the young Type Ia SNR 0509-67.5, we find that the size distribution of its small-scale substructures is consistent with the double-detonation explosion mechanism and further places constraints on the carbon─oxygen core mass and helium shell mass of the WD progenitor. The observed sizes of iron-dominated and sulfur-dominated substructures in SNR 0509─67.5 indicate a progenitor core mass and a shell mass of 1 M_⊙ and ≳0.05 M_⊙, respectively.

Characterisation of an EXor outburst SPICY 97589

First Author: Labdon, A.
Instruments: XSHOOTER
ProgramIDs: 112.26Z7, 113.28GX, 111.263U
BibCode: 2026A&A...709A..87L

Context. Stellar outbursts from variable or periodic accretion are thought to be ubiquitous across young stellar populations. However, relatively few outbursting objects have been discovered to date. Here, we present the characterisation of a new EXor-type episodic accretor. Aims. We aim to characterise the nature of the 2023 outburst of SPICY 97589(Gaia23bab) and characterise the stellar source for the first time, while exploring how an accretion outburst contributes to disk evolution. Methods. We employ multi-waveband medium-resolution spectroscopy with UVB-VIS-NIR coverage during the peak of the 2023 outburst and the post-outburst quiescent object. The broad wavelength coverage of the dataset allows for robust measurements of the accretion rate using known line tracers. The addition of quiescent spectra provides a good estimation of stellar parameters of the central star while also informing us about the evolution of the disk during outburst phases. Results. We find that the stellar source is a 3410 K, M3.0 type star with a luminosity of 0.41 L_⊙ and an estimated stellar mass of 0.29 M_⊙. We measure the accretion rate of SPICY 97589 to be Ṁ = 2.38 ± 0.58 × 10⁻⁷ M_⊙ yr⁻¹. This value is two orders of magnitude greater than the quiescent accretion rate. Thus, we confirm that the 2023 outburst was driven by an influx of material from the surrounding environment to the central star, an accretion outburst. The spectral fingerprint of the emission lines is also characteristic of an outbursting EXor-type source, including variable disk winds.

Spatial and spectral constraints on resolved mass loss of the massive post-red supergiant star IRAS 17163─3907 and its Fried Egg Nebula

First Author: Koumpia, E.
Instruments: CRIRES, FORS2, MATISSE
ProgramIDs: 107.22TZ, 111.24P0, 109.22VF
BibCode: 2026A&A...709A..83K

Context. The fate of massive stars during the latest stages of their evolution is highly dependent on their mass-loss rate and geometry. The geometry of the mass-loss process can be inferred from the shape of the circumstellar material, which has a significant influence on the evolution of massive stars (between 25 and 40 M_⊙), i.e. type II SN progenitors. In this context, post-red supergiants (post-RSGs) offer an excellent opportunity to study mass-loss events. Aims. We aim to investigate the mass-loss history, geometry, and physical conditions of the yellow hypergiant in a post-RSG stage, IRAS 17163−3907 (IRAS 17163, also known as the 'Fried Egg' nebula). We place it in context with another famous evolved massive star, the yellow hypergiant IRC+10420. Methods. We combine M-band spectra of the source using high-resolution CRIRES+ spectroscopy, with VLTI/MATISSE mid-infrared interferometry in the L-band, and FORS2 optical spectropolarimetry to probe both the small-scale circumstellar structure and the large-scale dusty environment of IRAS 17163. The interferometric observables were analysed with simple geometric fitting and a more advanced parametric modelling using PMOIRED to extract the morphology of the hot inner shell that was previously reported via radiative transfer modelling. Results. The CRIRES+ spectrum provides the first M-band coverage of IRAS 17163, revealing prominent low-excitation metal lines and hydrogen recombination features, but lacking the pronounced CO absorption seen in IRC+10420. The MATISSE observations reveal the first high angular scales of the source in the L-band and spatially resolve the Brα line-emitting region, which is a factor of two more extended than the continuum emission and hints at a marginally asymmetric and variable ionised wind. FORS2 spectropolarimetry shows intrinsic continuum polarisation and line effects in the Stokes Q parameter across Hα, pointing to deviations from perfect spherical symmetry also on larger scales. The interferometry reveals no evidence for a binary companion within the explored parameter space, indicating that the observed clumpy and time-variable mass loss is likely intrinsic to the star rather than companion-driven. Conclusions. Our results demonstrate that IRAS 17163 hosts a dense, structured, and time-variable wind, coexisting with extended dusty shells. Comparison with IRC+10420 highlights the diversity among post-RSG yellow hypergiants, with IRAS 17163 showing an ionised environment without apparent molecular signatures. These findings emphasise the role of clumpy and near-symmetric mass loss in shaping the circumstellar medium of evolved massive stars, with implications for their subsequent evolution and core-collapse supernova progenitor properties.

KiDS-Legacy: Constraining dark energy, neutrino mass, and curvature

First Author: Reischke, Robert
Instruments: OMEGACAM, VIRCAM
ProgramIDs: 177.A-3016, 177.A-3017, 177.A-3018, 298.A-5015, 179.A-2004
BibCode: 2026A&A...709A..82R

We constrained minimally extended cosmological models with the cosmic shear analysis of the final data release from the Kilo-Degree Survey (KiDS-Legacy) in combination with external probes. Due to the consistency of the KiDS-Legacy analysis with the cosmic microwave background (CMB), we could combine these datasets reliably for the first time. Additionally, we used CMB lensing, galaxy redshift-space distortions, and baryon acoustic oscillations. We assessed, in turn, the effects of spatial curvature, varying neutrino masses, and an evolving dark energy component on cosmological constraints from KiDS-Legacy alone and from KiDS-Legacy combined with external probes. We find KiDS-Legacy to be consistent with the fiducial flat Λ-cold dark matter (ΛCDM) analysis with c²∑m_ν ≤ 1.5 eV, w₀ = −1.0 ± 0.7, and w_a = −1.3_−2.0^+1.9 w a = − 1 . 3 − 2.0 + 1.9 while Ω_K = 0.8_−0.17^+0.16 Ω K = 0 . 08 − 0.17 + 0.16 (1σ bounds) with an almost equal goodness of fit. The w₀w_aCDM model is not a significant improvement over ΛCDM when cosmic shear and CMB lensing are combined, yielding a Bayes factor B = 0.07. If all probes are combined, however, B increases to 2.73, corresponding to a 2.6σ suspiciousness tension. The constraint on S₈ = σ₈√Ω_m/0.3 S 8 = σ 8 Ω m / 0.3 is robust to opening up the parameter space for cosmic shear. Adding all external datasets to KiDS-Legacy, we find S₈ = 0.816 ± 0.006 in ΛCDM and S₈ = 0.837 ± 0.008 in w₀w_aCDM for all probes combined.

High-contrast imaging of Galactic Cepheids with VLT/SPHERE

First Author: Gallenne, A.
Instruments: SPHERE
ProgramIDs: 0101.A-0214
BibCode: 2026A&A...709A..44G

Context. Classical Cepheids are key distance indicators and benchmarks for stellar evolution, yet most of them are members of binary or multiple systems. While spectroscopic surveys and Gaia proper-motion anomalies reveal a high binary fraction, the population of resolved companions remains poorly characterised. Aims. We aim to search for and characterise visual companions to bright Galactic Cepheids using high-contrast imaging and to derive quantitative limits on undetected companions to constrain the architecture of Cepheid multiple systems. Methods. We observed 47 Galactic Cepheids with VLT/SPHERE using the ZIMPOL instrument in classical imaging mode and the V, R', and I' filters. The data were obtained in pupil-stabilised mode and analysed using PCA-based imaging technique. For detected companions, we injected negative fake companions in a Monte Carlo approach to measure the relative astrometry. For non-detections, synthetic companions were injected to compute 5σ contrast curves as a function of separation. Results. We detected companions with a signal-to-noise ratio of S/N > 5 for eight Cepheids (η Aql, AX Cir, S Nor, AP Pup, W Sgr, T Vel, TX Del, and V659 Cen), corresponding to about 17% of the sample. Our SPHERE imaging confirms previously known visual companions with improved astrometry and reveals new wide components for AP Pup, T Vel, and TX Del) at projected separations of ∼0.16 − 0.9″. For the remaining Cepheids, we derived typical maximum contrasts of ∼10, 11, and 12 mag at 0.25″, 0.5″, and > 1″, respectively. For a sub-set of targets, these limits ruled out main sequence companions more massive than late-K dwarfs beyond 0.5″. Conclusions. Our SPHERE survey provides the first homogeneous set of high-contrast optical constraints on wide companions of Galactic Cepheids. The low detection rate of visual companions compared to the high overall binary fraction implies that most companions inferred from radial velocities and Gaia astrometry are either closer than ∼20 mas or significantly fainter than the limits reached here.

A z ∼ 1 galactic-scale outflow transversally mapped to ∼ 50 kpc through gravitational-arc tomography

First Author: Hernandez-Guajardo, J. A.
Instruments: MUSE
ProgramIDs: 094.A-0141
BibCode: 2026A&A...708A.376H

We report spatially resolved measurements of cool gas traced by Mg II and Fe II absorption in the circumgalactic medium (CGM) of a star-forming galaxy at z ∼ 1 (G1). The fortuitous alignment of a background gravitational arc at z ∼ 2.4 provides seven closely spaced (∼6 kpc) transverse sightlines along the minor axis of G1, probing its CGM out to ∼50 kpc. This geometry allowed us to detect a galactic-scale outflow simultaneously in the down-the-barrel and transverse directions, where we detected blueshifted Mg II absorption lines along both types of sightlines, revealing a large-scale collimated wind. We measured blueshifted line-of-sight velocities of v_los ∼ 62 − 239 km s⁻¹ and line-of-sight velocity dispersions of σ_los ∼ 53 − 133 km s⁻¹, suggesting a structure dominated by bulk motion. De-projection of v_los along the minor axis indicates that the outflow material barely approaches the escape velocity and is likely to be gravitationally bound to G1. We constrained an outflow opening angle θ_c ∼ 18° −25°, and a mass outflow rate of Ṁ_out ≳ 0.06 M_⊙ yr⁻¹, corresponding to a mass loading factor η ≳ 0.004, estimated within ∼10 − 50 kpc (∼0.05 − 0.3 R_vir) of the galaxy centre. Our measurements, combined with previous arc tomography data along the major axis, indicate that normalizing impact parameters by galaxy B-band luminosity substantially reduces scatter in the established anti-correlation between Mg II equivalent width and impact parameter, while also diminishing possible excess of Mg II equivalent width towards the minor axis. ★ Based on observations collected at the European Southern Observatory under ESO programme 094.A-0141 (MUSE).

Unveiling large-scale rotational motions in the intragroup medium at z ∼ 1 through gravitational-arc tomography

First Author: Ledoux, Cedric
Instruments: MUSE
ProgramIDs: 098.A-0459
BibCode: 2026A&A...709A..18L

Context. The circumgalactic medium (CGM) is a crucial interface between galaxies and their large-scale environment, regulating gas accretion and feedback processes. Yet its physical and kinematic properties within galaxy groups, where most galaxies reside, remain poorly constrained. Aims. We present the first spatially resolved characterisation of the cool intragroup medium (IGrM) in a spectroscopically confirmed galaxy group at z ≃ 1.167 using absorption-line spectroscopy along multiple sightlines. Methods. Using 30 independent sightlines towards the gravitationally lensed galaxy SGAS J003341.5+024217, we combined background light from an extended gravitational arc and various sources in the field to map the distribution and kinematics of diffuse metal-enriched gas pertaining to this group. Results. We detected prominent Mg II, Fe II, Ca II, and Mg I absorption extending up to a projected distance of 62 kpc from a massive (log M_★ = 11.0 ± 0.1 M_⊙) star-forming spiral and its interacting companion. Together with four other members, these form a compact group with a virial radius of 313 kpc. Down-the-barrel, blueshifted absorption indicates outflows. The distribution and two-dimensional kinematics of this gas suggest the influence of both tidal stripping and star formation-driven winds. Intervening absorption across the field partly traces internal galaxy motions. A simple superposition of individual discs cannot reproduce the velocity field at large impact parameters or in counter-rotating regions, while a global IGrM halo with a rotational velocity of ≍130 km s⁻¹ provides a good match. Beyond individual galaxy envelopes, we find the data to be consistent with a group-scale structure that co-rotates in concert with the galaxies. Assuming dynamical equilibrium, we estimated a total (cool+warm+hot) gas mass of 1.3 − 2.5 × 10¹¹ M_⊙, with large systematic uncertainties, corresponding to roughly 50% of all baryons within one-quarter of the group's virial radius. Conclusions. These results point to a multiphase IGrM in which cool (∼10⁴ K) clouds are embedded within a dynamically coherent group-wide halo. The gas appears to be gravitationally bound to the group rather than reaccreting onto individual galaxies. High-redshift strong Mg II absorbers may thus trace shared metal-enriched halos shaped by galaxy interactions and feedback, with stripped and outflowing gas accumulating in the IGrM over time. ★ Based on observations carried out in service mode at the European Southern Observatory (ESO) under programme ID 098.A─0459(A).

UGC 2369S: A Kiloparsec-scale Triple Merger Candidate Identified in a Nearby Luminous Infrared Galaxy

First Author: Ding, Yuanze
Instruments: MUSE
ProgramIDs: 108.22C1
BibCode: 2026ApJ..1002..130D

We present high-spatial-resolution (≲1 .″ 0), multiwavelength observations of UGC 2369S, a nearby luminous infrared galaxy showing three distinct cores separated on kiloparsec scales in near-infrared (NIR) imaging with significant X-ray emission. Utilizing optical/NIR adaptive optics, radio, Chandra X-ray, as well as archival Hubble Space Telescope imaging, we perform a comprehensive study of active galactic nuclei (AGN) activity, obscuration, and host properties. As one of the clearest cases of a triple-nucleus merger at ≃3 kpc separations, UGC 2369S is the first to be studied with high-resolution observations at multiple wavelengths. We find that the northern core, having possibly the most massive black hole (BH) in the system (M_BH ≃ 10⁸ M_⊙), is consistent with a heavily obscured AGN. However, its high dust extinction (A_v > 5), hydrogen column density (N_H ≳ 10²⁵ cm⁻²), and nondetection of optical coronal lines and coronal X-ray emission leave the identification inconclusive. The other two cores show no evidence for black-hole activity and instead exhibit signatures of tidal disruption. From stellar mass surface density and stellar velocity dispersion maps, we infer that the strongly varying gravitational potential in this three-body system may have cannibalized the stellar bulge of the southwestern core, leaving a metal-enriched remnant. An ongoing survey focusing on similar triple systems could help us understand how they evolve and help benchmark numerical simulations, providing insight into gravitational wave predictions and the formation of the most massive BHs.

Blue Straggler in the Making: An X-Ray Active Binary in Algol Configuration

First Author: Sheikh, A. H.
Instruments: FLAMES, GIRAFFE
ProgramIDs: 109.22ZM
BibCode: 2026ApJ..1002L..29S

We report an extremely rare X-ray active blue straggler star (BSS) in Collinder 261, undergoing ongoing Roche-lobe overflow in a semidetached binary in an Algol-type configuration with an orbital period of P_orb ∼ 2.112 days, providing direct observational evidence for the ongoing binary mass-transfer formation channel of BSS. Light-curve modeling with PHOEBE reveals a low mass ratio of q ∼ 0.19, corresponding to a mass of 1.67 M_⊙for the BSS primary and a mass of 0.32 M_⊙ for the Roche-lobe-filling companion. Reflection effects and a hotspot near the inner Lagrangian point (L₁) reproduce the observed light-curve asymmetries, while the observed X-ray luminosity is consistent with direct-impact accretion-driven emission, supporting ongoing mass transfer. Radial velocities from the Very Large Telescope/GIRAFFE are also consistent with the photometric solution and reveal enhanced primary rotation of vsini∼69.55 km s⁻¹, consistent with spin-up through direct-impact accretion. Evolutionary modeling with MESA reproduces the observed configuration for an initially detached system with M_d ∼ 1.12 M_⊙, M_a ∼ 0.92 M_⊙, and P_ini ∼ 0.83 day. Roche-lobe overflow and mass transfer begin at ∼5.46 Gyr with mass ratio reversal at ∼5.58 Gyr. The present configuration at ∼7 Gyr, consistent with the cluster age, corresponds to stable mass transfer of Ṁ∼ 2 × 10⁻¹⁰ M_⊙ yr⁻¹. These results indicate that the system represents a very rare case of a BSS currently forming through binary mass transfer.

No country for old stars: Spectroscopic confirmation of the first intermediate-age RR Lyrae in the open cluster Trumpler 5

First Author: D'Orazi, V.
Instruments: UVES
ProgramIDs: 074.D-0344
BibCode: 2026A&A...708L..22D

Context. RR Lyrae (RRL) stars are widely considered tracers of ancient (> 10 Gyr) metal-poor stellar populations. However, recent kinematic and photometric studies suggest the existence of a metal-rich RRL subpopulation associated with the thin disk and intermediate ages (∼2─5 Gyr), therefore challenging canonical evolutionary models. Aims. We aim to provide the first spectroscopic confirmation of a member of this elusive population. Specifically, we target a metal-rich RRL candidate recently identified photometrically as a member of the intermediate-age open cluster Trumpler 5 (∼2.5 Gyr). Methods. We obtained high-resolution spectroscopy using PEPSI at the LBT and GHOST at Gemini South telescope. We measured radial velocities (RVs) from multiple epochs to constrain cluster membership and derived detailed chemical abundances (Mg, Ca, Sc, Ti, Mn, Fe, Cu, Zn, Y, and Ba) to compare the RRL's composition with that of red clump stars in the cluster. Results. The RRL's systemic velocity ( V_γ = 50.57^+0.78_−0.36 V γ = 50 . 57 − 0.36 + 0.78 km s⁻¹) is in excellent agreement with the cluster mean (V = 50.76 ± 0.49 km s⁻¹). Combining RVs, proper motions, and parallax, the probability of the star being a background interloper is negligible (∼0.002%, better than 4σ). We derived a metallicity of [Fe/H] = −0.40 ± 0.05, which matches the cluster value. While most abundance ratios (Mg, Ti, Mn, Cu, and Zn) align with cluster members, the RRL exhibits significant depletion in Ca, Sc, Y, and Ba. Notably, [Sc/Fe] is underabundant by ∼0.6 dex relative to the cluster stars, following trends seen in field metal-rich RRLs. Conclusions. We provide strong constraints on the membership status between an RRL variable and an intermediate-age open cluster. Cluster membership enables accurate measurement of RRL age and chemical anomalies relative to its host, particularly in Sc and neutron-capture elements. These anomalies further reinforce a nonstandard formation channel for this RRL, possibly indicating binary interactions and mass transfer.

The GECKOS Survey: extraplanar ionized gas in star-forming galaxies from eDIG to galaxy-scale winds

First Author: Elliott, R.
Instruments: MUSE
ProgramIDs: 110.24AS
BibCode: 2026MNRAS.548ag672E

We map the extraplanar gas, with

$\sim$

50─200 pc resolution, in nine star-forming galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Programme targeting edge-on galaxies with similar stellar mass as the Milky Way. The narrow range in stellar mass (

$\pm 0.35$

dex) of the GECKOS sample makes it ideal for studying trends with star formation rate (SFR). We find strong extraplanar emission reaching

$\sim$

2-8 kpc from the disc mid-plane in all targets with

$\rm {SFR}\ge$

1 M

$_{\odot }$

$^{-1}$

. Targets with SFR

$\, \ge \,$

5 M

$_{\odot }$

$^{-1}$

have brighter, more extended H

$\alpha$

emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion (

$\sigma _{\rm H\alpha }$

) shows a biconical morphology, consistent with the expectation of outflows. This agrees with previous works suggesting high velocity dispersion in a biconical shape is a good means to identify outflows. We find mixed results using line diagnostics ([O III]

$_{5007}$

$\beta$

─[N II]/H

$\alpha$

and

$\sigma _{\rm H\alpha }$

─[S II]/H

$\alpha$

) to spatially resolve ionization mechanisms across the extraplanar gas. The highest [N II]/H

$\alpha$

are found in the extraplanar gas of the highest SFR systems, yet main-sequence galaxies have the highest [O III]/H

$\beta$

. While the morphology of [N II]/H

$\alpha$

may be useful to identify outflows, the absolute value of the line ratio alone may not distinguish strong outflows from extraplanar gas of main-sequence galaxies. The ubiquitous extraplanar emission can be interpreted as the result of feedback, in the form of large-scale winds for starbursts or smaller-scale galactic fountains for main-sequence galaxies. Moreover, shock-heating may ionise gas at the interface of the disc and the circumgalactic medium, independent of the source of the gas.

STEP survey: III. STEPping stones between the clouds: the star formation history of the Magellanic Bridge

First Author: Ficara, F.
Instruments: OMEGACAM
ProgramIDs: 088.D-4014, 092.D-0214, 091.D-0574, 090.D-0172, 094.D-0492, 099.D-0673, 098.D-0579, 096.D-0535, 095.D-0132, 097.D-0209, 093.D-0174, 089.D-0258
BibCode: 2026A&A...709A..10F

Context. The Magellanic Clouds (MCs) offer a unique laboratory for studying galaxy interaction and the evolution of dwarf galaxies. The star formation history (SFH), which traces when and how stars formed, provides powerful constraints for the dynamical modelling of the system's past interactions and the processes of stripping and triggered star formation in tidally influenced environments. Aims. We aim to reconstruct the SFH of the Magellanic Bridge, the gaseous and stellar stream connecting the Magellanic Clouds. We used data from the deep optical STEP survey, which covers 54 deg² across the Small Magellanic Cloud (SMC) and the Bridge, reaching stars below the oldest main-sequence turnoff at the distance of the MCs. Methods. We applied the synthetic colour-magnitude diagram technique to 14 deg² of STEP data. We constructed two libraries of synthetic stellar populations based on the PARSEC-COLIBRI and BaSTI stellar evolutionary models, with metallicities in the range −2.0 ≤ [Fe/H] ≤ 0 across the whole Hubble time. Results. We find a clear peak of recent star formation ∼100 Myr ago in the Magellanic Bridge, which becomes increasingly pronounced towards the SMC. The low metallicity of this population suggests that it formed from gas stripped from the SMC during its most recent close encounter with the LMC. In the eastern part of the Bridge (LMC side), star formation peaks at earlier times, around 10 Gyr and 2 Gyr ago. We estimate a total stellar mass in the Bridge of (5.1 ± 0.2) × 10⁵M_⊙ and a present-day stellar metallicity of [Fe/H]~-0.6 dex, close to SMC value.

Discovery of planetary-mass binaries in the Lower Centaurus-Crux association

First Author: Caceres, Claudio
Instruments: VIRCAM
ProgramIDs: 198.B-2004, 179.B-2002
BibCode: 2026A&A...708A.378C

Context. The recent discovery of free-floating planets (FFPs) in nearby young stellar associations suggests that these objects might be common in the Galaxy. Our search for FFPs in the young Lower Centaurus-Crux (LCC) association using the VISTA Variables in the Vía Láctea VVV and VVVX surveys revealed several candidates with distances d < 200 pc. Aims. The main goal of the paper is to identify binary FFPs among this sample. The presence of such binaries is useful to contrast two different main formation scenarios: the formation in the circumstellar disk of the parent star with subsequent ejection by dynamical interactions and the in situ formation by gravitational collapse of a protostellar cloud. Methods. We used the Gaia, VVV, VVVX, and DECaPS databases to identify pairs of low-mass objects in the LCC association sharing common proper motions. We examined the optical and near-IR color-magnitude and color-color diagrams, and visually confirmed the detections in the available optical and near-IR images. Results. We find 17 young low-mass binaries in the LCC association, with distances starting from 68 pc and projected separations ranging from 88 to 6742 au. A couple of candidates have additional faint companions that need confirmation to secure them as triple systems. Adopting an age of 17 Myr for the LCC association, we find that 14 of the components are faint enough to have planetary masses. Conclusions. Our results indicate that binaries represent ≳2% of the population of FFPs in the LCC association, and this suggests that their preferred formation mechanism is the gravitational collapse independent of a star. Also, many of the recently discovered FFPs in LCC may be unresolved giant binary planets. The wide range of colors and flux reversals observed suggests that the existence of clouds in their atmospheres is important and points to continuity with the BD populations.

Beyond compactness: A structural─dynamical─evolutionary manifold for the stellar-to-dynamical mass ratio in ultra-compact massive galaxies

First Author: Spiniello, Chiara
Instruments: XSHOOTER
ProgramIDs: 1104.B-0370
BibCode: 2026A&A...709A..33S

Context. Ultra-compact massive galaxies (UCMGs) often exhibit elevated stellar-to-dynamical mass ratios when dynamical masses are estimated using standard virial prescriptions. This discrepancy has been interpreted as evidence for structural non-homology driven primarily by their compactness. Aims. This study investigates how the stellar-to-dynamical mass ratio depends on compactness (𝒞), internal kinematics (σ_★), stellar population properties (mass-weighted age, metallicity, and [Mg/Fe]), and star formation histories. The analysis is based on a homogeneous catalogue of 482 UCMGs from the INSPIRE and E-INSPIRE surveys, extending to significantly smaller sizes than previously analysed samples. Methods. I first derive the compactness─mass relation assuming a constant virial coefficient (K = 5). I then correct stellar masses for initial mass function (IMF) variations and recompute stellar-to-dynamical mass ratios using an empirical prescription in which the virial coefficient varies as a function of radius and stellar mass. Finally, I test whether the relation is modulated by stellar kinematics and population properties, including the degree of relicness (DoR), which quantifies the extremeness of the star formation history. Results. A statistically significant anti-correlation between compactness and the IMF-corrected stellar-to-dynamical mass ratio is recovered when a constant virial coefficient is adopted, even within the relatively narrow range of 𝒞 spanned by nearby UCMGs. The relation substantially flattens when a structure-dependent K is adopted, in agreement with previous literature. Beyond this one-dimensional behaviour, the data define a structural─dynamical manifold in the (log𝒞, log σ_★) space. Velocity dispersion sets the dominant axis of variation, and the corresponding plane accounts for ∼62% of the variance in stellar-to-dynamical mass ratio. Including stellar age increases the explained variance to ∼63%, revealing a secondary evolutionary modulation. In contrast, DoR, metallicity, and [Mg/Fe] do not retain independent explanatory power once stellar age is included. Conclusions. The stellar-to-dynamical mass ratio in UCMGs is governed primarily by the depth of the gravitational potential, traced by stellar velocity dispersion, rather than by compactness alone. At fixed size, systems with higher σ_★ exhibit systematically lower stellar-to-dynamical mass ratio, indicating that dynamical structure regulates the apparent mass imbalance in the ultra-compact regime. Compactness largely reflects this dynamical scaling, while stellar age introduces a coherent secondary modulation linking the structural manifold to the evolutionary state of the galaxy. Non-homology in UCMGs therefore encodes coupled dynamical and assembly processes rather than purely geometric compactness.

Changing-look Active Galactic Nuclei in SDSS-V: Host-galaxy Properties and Black Hole Scaling Relations

First Author: Zeltyn, Grisha
Instruments: XSHOOTER
ProgramIDs: 114.27B8, 112.25S8
BibCode: 2026ApJ..1002...61Z

Changing-look active galactic nuclei (CL-AGNs) exhibit dramatic spectral variability on unexpectedly short timescales, challenging standard accretion flow models. Despite growing samples, the physical drivers of this extreme variability, and the potential link to host-galaxy properties, remain unknown. Regardless of the underlying mechanism, the transition between AGN-dominated and host-dominated spectra offers a unique opportunity to study relations between AGNs and their hosts within the same objects. We present intermediate-resolution spectroscopy of 23 CL-AGNs identified by the Sloan Digital Sky Survey V (SDSS-V), obtained with the Very Large Telescope/X-shooter and Gemini-N/GMOS. An analysis of the Mg II λ2798 emission line observed in the spectra demonstrates that the majority of these sources cannot be driven by variable obscuration. Our CL-AGNs roughly follow the M_BH─σ_* and M_BH─M_* relations of inactive galaxies, with a median black hole-to-stellar mass ratio of 0.38 %. We find no evidence that the stellar population properties of our CL-AGNs, including stellar mass, age, young stellar fraction, and star formation rate, differ from those of type 2 AGNs in SDSS. These results suggest that CL-AGNs reside in typical AGN host galaxies and that their extreme variability is likely unrelated to host-galaxy environment, supporting the idea that CL-AGNs are not a distinct population, but rather represent a phase of normal AGN activity. This result, in turn, implies that CL-AGNs can serve as useful probes of the AGN-host connection, providing access to both AGN-dominated and host-dominated spectra of the same systems.

The GRAVITY young stellar object survey: XV. The star-disk interaction region of the T Tauri star DO Tau

First Author: Gravity Collaboration
Instruments: GRAVITY
ProgramIDs: 110.23TT, 112.25T1
BibCode: 2026A&A...708A.334G

Context. Protoplanetary disks around young Sun-like stars are the cradles of the vast majority of detected exoplanets. Probing these disks at multiple spatial scales is key to uncovering how planets form. The inner astronomical unit, the star-disk interaction region, is of utmost importance because most detected exoplanets occupy this zone. Aims. We aim to spatially and spectrally resolve the inner disk and star-disk interaction region of the M0.3 T Tauri star DO Tau by combining two complementary techniques. Methods. We used high-resolution near-infrared spectra from CFHT/SPIRou to constrain the magnetospheric star-disk interaction process and optical long-baseline interferometry with ESO VLTI/GRAVITY to determine the sizes of the K-band continuum and Brγ line emitting regions. From the SPIRou spectra, we measured the veiling in the YJHK bands along with the equivalent widths of the HeI λ1083, Paβ, and Brγ emission lines, from which we estimated the mass accretion rate. We were able to monitor the time variability of these quantities thanks to our long-sequence of observations over about 40 days. We fit the GRAVITY visibilities in the continuum and the differential quantities in the line with geometrical models to obtain the orientation and the size of the inner disk as well as the size and the on-sky displacement of the Brγ emitting region. Results. We derived a mass accretion rate of ∼10⁻⁸−10⁻⁷ M_⊙ yr⁻¹, which confirms that this ∼0.5 M_⊙ star is a strong accretor. The HI and HeI lines exhibit strong variability on a daily timescale, consistent with the burster classification of DO Tau derived from its K2 light curve. We report a periodic modulation of the intensity of the redshifted high-velocity wings of the Brγ line profile. The modulation occurs at the rotational period of the star (5.128 d), which suggests the existence of corotating magnetospheric funnel flows. We derived an upper limit of 0.35 on the ratio between the magnetospheric truncation radius and the disk corotation radius, indicative of an ordered unstable accretion regime. The size of the Brγ line emitting region obtained from GRAVITY is quite small (R_Brγ = 0.011 au ∼ 1.3 R_*), and it is much smaller than the K-band continuum emitting region (R_K = 0.09 au ∼ 11 R_*). Such a compact Brγ emission region suggests that most of the line flux originates from the magnetospheric accretion region and/or from an inner wind close to the magnetosphere-disk interface. The on-sky displacements of the blue and red Brγ line velocity channels suggest a rotation pattern of the emitting gas, as they appear to be nearly aligned along the position angle of the disk. The inclination we derived for the inner disk (∼45-55°) differs from that of the outer disk inferred from the ALMA continuum (∼30°). This points toward a misalignment or warp of the outer disk that may originate from the suspected past encounter with the neighboring HV Tau system. Conclusions. Based on combining high-resolution spectroscopy and long baseline interferometry, we find that the T Tauri star DO Tau appears to be a strong accretor undergoing magnetospheric accretion in an ordered unstable regime, with a Brγ line emitting region as compact (∼0.01 au) as the size of its magnetosphere.

Estimating the completeness of the QUBRICS survey with 3501 quasi-stellar object redshifts from Gaia DR3 spectra

First Author: Porru, Matteo
Instruments: EFOSC2
ProgramIDs: 114.27HT
BibCode: 2026A&A...708A.363P

Context. Quasi-stellar objects (QSOs) are essential for investigating the structure and evolution of the Universe. Historically, their identification has been concentrated in the northern hemisphere, primarily due to the sky coverage of major astronomical surveys. The QUBRICS (QUasars as BRIght beacons for Cosmology in the Southern hemisphere) survey, started in 2019 to address this asymmetry, has identified more than 1300 new bright (i < 19.5) high-redshift (2.5 < z < 6) QSOs in the southern sky. Aims. This study aims to quantify, using an independent QSO sample, the completeness and recall of the QUBRICS QSO selection methods, based on extreme gradient boosting (XGB) and probabilistic random forest (PRF) techniques, since completeness is a fundamental metric for ensuring the statistical robustness of QSO-based cosmological investigations. Methods. We analyzed a subset of Gaia DR3 sources (G < 18.25, |b| > 25 deg, negligible parallax and proper motion) with low-resolution spectra, from which we obtained a sample of 3501 QSOs. To determine how many QSOs were correctly identified as candidates, we crossmatched this independent sample with the datasets used for selection: 894 QSOs with z > 2.5 fell within the XGB dataset footprint, of which 152 were unclassified and thus eligible for completeness testing. Similarly, 675 QSOs with z > 2.5 were within the PRF dataset footprint, including 69 unclassified objects. Results. The XGB correctly identified as candidates 136 (89%) of the 152 QSOs with z > 2.5 listed in the XGB dataset as unclassified objects. The PRF correctly identified as candidates 46 (66%) of the 69 QSOs with z > 2.5 listed in the PRF dataset as unclassified objects. Conclusions. These findings confirm the high efficiency of the QUBRICS selection methods (recall = 89%) and provide the completeness estimate for spectroscopically confirmed QSOs (82%), which is necessary for cosmological studies that use QUBRICS data. This work also provides reliable redshifts for 1223 new QSOs (median redshift z = 2.1 and magnitude G = 17.8), which will help improve the performance of future selections.

Cosmology with supernova Encore in the strong lensing cluster MACS J0138─2155: Lens model comparison and H₀ measurement

First Author: Suyu, S. H.
Instruments: MUSE
ProgramIDs: 0103.A-0777, 110.23PS
BibCode: 2026A&A...708A.291S

Robust mass modeling of strong-lensing galaxy clusters is crucial for studying cosmology and galaxy evolution. We present and compare seven mass models of the galaxy cluster MACS J0138−2155, constructed using six independent modeling software programs, including parametric and free-form approaches. By conducting a blind analysis where all the mass-modeling teams constructed their models independently without exchanging results, we quantified uncertainties arising from modeling software and assumptions. MACS J0138−2155 is unique as the only cluster found to strongly lens two supernovae (SNe), Requiem and Encore, from the same host galaxy at a redshift of z = 1.949, providing an excellent probe of cosmology through time delays between their multiple images. Through the Hubble Space Telescope, James Webb Space Telescope, and Multi Unit Spectroscopic Explorer observations, we assembled high-quality data products, including eight sets of "gold" lensed-image systems consisting of 23 multiple images with secure spectroscopic redshifts. We further identified one "silver" lensed-image system with a likely but nonsecure redshift measurement. By restricting ourselves to high-quality gold images, we obtain overall good consistency in the model predictions of the positions, magnifications, and time delays of the multiple images of SN Encore and SN Requiem ─ especially from the teams whose models fit the observed image positions with χ_im² ≤ 25. We predict the next images of SNe Encore and Requiem to reappear with time delays ≳3000 days and ∼3700 to 4000 days, respectively, based on a fiducial cosmological model with H₀ = 70 km s⁻¹ Mpc⁻¹ and Ω_m = 1 − Ω_Λ = 0.3. By considering a range of hypothetical time-delay values with the same Ω_m = 1 − Ω_Λ = 0.3, we obtain relations between H₀ and the time delays of SN Encore and SN Requiem. In particular, for H₀ = 73 km s⁻¹ Mpc⁻¹, the four lowest χ_im² models forecast the next image of SN Requiem to appear approximately April─December 2026; for H₀ = 67 km s⁻¹ Mpc⁻¹, they predict it to appear approximately March─November 2027 (1σ uncertainties). Using the newly measured time delay between the two detected multiple images of SN Encore by Pierel et al. (2026, ApJ, 998, 219) and our mass modeling, we infer H 0 = 66 . 9 − 8.1 + 11.2 km s⁻¹ Mpc⁻¹, where the uncertainty is dominated by that of the short time delay between the existing pair of images. The long time delays of the next-appearing SN Requiem and SN Encore images provide excellent opportunities to measure H₀ with 2−3% uncertainty. Our mass models form the basis for cosmological inference from this unique lens cluster with two strongly lensed SNe.

Reconciling near-infrared and microwave analyses of Neptune's hydrogen sulphide distribution

First Author: Penn, Joseph
Instruments: SINFONI
ProgramIDs: 0101.C-0081
BibCode: 2026MNRAS.548ag688P

Previous analysis of Neptune's atmosphere using near-infrared Gemini/NIFS observations found the strongest spectral signature of hydrogen sulphide (H

$_2$

S) to be at the planet's south pole. Conversely, analysis of microwave observations with the Atacama Large Millimeter/submillimeter Array in 2019 suggested a distribution of H

$_2$

S that peaks in the mid-latitudes and is strongly depleted towards the pole. We analyse near-infrared observations from VLT-SINFONI in 2018 and fit a parametrized cloud model to the data using nested sampling. By prescribing a latitudinally varying methane (CH

$_4$

) profile previously derived from visible light observations, we find general agreement with the microwave analysis, with an enhancement of H

$_2$

S by a factor of

$\sim$

4 at the southern mid-latitudes compared to polar latitudes. The stronger spectral signature at the pole is explained with a deeper cloud top, resulting in a higher cloud-top H

$_2$

S column abundance in this region. Our results are indicative of deep upwelling at the mid-latitudes, with downwelling at the pole and possibly near the equator.

Helium emission from Balmer-dominated shocks in Type Ia supernova remnants provides constraints to their progenitor systems

First Author: Das, Priyam
Instruments: MUSE
ProgramIDs: 0100.D-0151, 0104.D-0104, 096.D-0352
BibCode: 2026MNRAS.548ag596D

Balmer-dominated shocks in Type Ia supernova remnants offer powerful probes into collisionless shock physics and hints towards supernova progenitor environments. Prior studies focused on the hydrogen Balmer lines, which manifest as a superposition of broad and narrow emission lines. Using integral-field spectroscopy with Multi Unit Spectroscopic Explorer (MUSE), we discovered broad and narrow helium emission lines from Balmer-dominated filaments of three Type Ia supernovae remnants in the Large Magellanic Cloud: SNR 0509-67.5, SNR 0519-69.0, and N103B. We detect broad and narrow He I 5876 Å, 7065 Å emission in SNR 0519 and N103B and He II 8236 Å in SNR 0519. In SNR 0509, we detect narrow He I 5015 Å, 6678 Å, 7065 Å, and 7281 Å, with only 7065 Å exhibiting a broad component. The detection of narrow He II challenges existing shock models, where such emission is not expected, and may indicate either incomplete ion─ion equilibration behind the shock or an origin in shock precursors. For SNR 0509 and N103B, the neutral He/H line ratios indicate enhanced helium abundances, whereas SNR 0519 is consistent with the primordial He/H value. We therefore propose helium emission in Balmer-dominated shocks as a new diagnostic of shock physics and Type Ia supernova circumstellar environments. Although our modelling is primarily a proof of concept, it demonstrates the possibility to infer the total He-to-H abundance ratio, with dominant uncertainties arising from the assumed initial ionization fractions. Despite the uncertainties, we demonstrate that narrow helium lines can serve as effective probes of circumstellar conditions and progenitor evolution when analysed alongside reliable constraints on the pre-shock neutral H/He abundance ratio.

Observational constraints on the chemical tracers of planet formation history: A systematic survey of 13 directly imaged low-mass companions with VLT/ERIS

First Author: Hayoz, J.
Instruments: ERIS
ProgramIDs: 112.2628
BibCode: 2026A&A...708A.312H

Context. Constraining the link between the atmospheric composition of giant exoplanets and their formation history is a key goal of exoplanet studies. In particular, the atmospheric carbon-to-oxygen (C/O) ratio and metallicity ─ which are readily measurable with direct spectroscopic observations ─ are believed to be chemical tracers of the birth location of substellar and planetary companions. Aims. We aim to collect observational constraints for planet formation theories by performing a large and systematic survey of the atmospheric C/O ratio and metallicity. Methods. We collected new K-band moderate-resolution (R ~ 11 000) spectroscopic observations of 13 directly imaged planetary-mass companions spanning the molecular snowlines of CO₂, CO, and CH₄ and with masses 4─30 M_J with VLT/ERIS/SPIFFIER. Additionally, we gathered a large portion of the available archival observations for these targets, amounting to 40 spectra and 140 photometric fluxes. We performed spectral fits using self-consistent grid models and freely parametrisable models. We obtained robust estimates of the key atmospheric parameters by aggregating the results from the different models, thereby reducing modelling systematics. Results. Using molecular mapping, we detected H₂O and CO in 12 of our targets as well as ¹³CO in HR 2562 B. With our multimodel spectral fitting strategy, we obtained stellar to superstellar C/O ratios ─ ranging between 0.3 and 0.8 ─ and predominantly superstellar metallicities ─ between −1 and 1 dex ─ across all targets. We measured a substantial enrichment of ¹³CO for HR 2562 B with ¹²CO/¹³CO= 12.0_−3.3^+4.5. If corroborated by independent observations, it could indicate that the companion might have formed beyond the CO snowline and later migrated inwards to its current location. We find an anti-correlation (R = −0.64) between the C/O ratio and the companion mass, consolidating a previous result. Conclusions. Our work demonstrates the scientific potential of the ERIS/SPIFFIER instrument for the orbital and atmospheric characterisation of close-in substellar and exoplanet companions.

UVIT Magellanic BRidge Analysis (UMBRA) ─ I. Far-UV─Gaia study of seven star clusters

First Author: Choudhury, Samyaday
Instruments: VIRCAM
ProgramIDs: 179.B-2003, 0103.B-0783, 0103.D-0161, 099.C-0773, 099.D-0194, 105.2042, 106.2107, 108.222A, 108.223E, 109.230A, 109.231H, 110.259F, 0100.C-0248
BibCode: 2026MNRAS.548ag594C

We present the first high spatial resolution far-ultraviolet (FUV; F148W) images of seven star clusters in the Magellanic Bridge using the UltraViolet Imaging Telescope (UVIT) on the Indian multiwavelength space observatory AstroSat. These observations emphasize UVIT's unique capability to resolve individual stellar populations at the distance of the Magellanic Clouds (50─60 kpc). Using probable cluster members, we constructed colour─magnitude diagrams using UVIT and Gaia data to estimate key cluster parameters such as age, distance, and extinction. We assessed the likelihood that these are genuine star clusters and carried out stellar parameter estimation of individual hot main-sequence (MS) stars. Our analysis confirms that four objects, BS 245, L 144, OGLE-MBR-CL-0075, and OGLE-MBR-CL-0084, are bona fide clusters. The remaining objects are likely OB associations or field stars. For three, OGLE-MBR-CL-0026, OGLE-MBR-CL-0030, and OGLE-MBR-CL-0084, we provide age estimates for the first time. All seven objects have ages between 15 and 70 Myr, supporting an in situ star formation scenario triggered by tidal interactions between the Magellanic Clouds. We further model the spectral energy distribution of 51 MS stars by combining photometric data from UVIT, the GALaxy Evolution eXplorer (GALEX), Gaia, and two near-infrared surveys: the VISTA Survey of the Magellanic Clouds and Two Micron All Sky Survey. The modelling reveals five hot MS stars with

$T_{\mathrm{eff}}$

ranging between 32 500 (

$\pm$

1250) K to 42 500 (

$\pm$

1250) K and

$\log g$

from 3.5 (

$\pm$

0.1) dex to 4.0 (

$\pm$

0.1) dex, consistent with late O-type stars. We release an FUV photometric catalogue of all MS stars to enable future studies of stellar abundances and binarity in the Bridge.

A Kiloparsec-scale Stellar Cavity in the Center of A402-BCG May Be Caused by Dynamic Interactions with an Ultramassive Black Hole

First Author: McDonald, Michael
Instruments: MUSE
ProgramIDs: 0100.A-0249, 099.A-0292, 0103.A-0157
BibCode: 2026ApJ..1002L..19M

We present new observations from JWST that reveal a striking kiloparsec-wide cavity in the stellar distribution of the central galaxy in the cluster A402. Supporting data from the Hubble Space Telescope (HST) allow us to rule out extinction due to dust as an explanation, and instead, suggest that this is a localized depression in the stellar density field corresponding to ∼2 × 10⁹ M_⊙ in missing stars within a volume of 0.5 kpc³. On larger scales, both the JWST and HST data show evidence for a 2.2 kpc flattened core in the stellar distribution (on which the smaller-scale cavity is superimposed), which implies the presence of a central ultramassive black hole with M_BH ∼ 5 × 10¹⁰ M_⊙. We report evidence for a mid-IR-bright point source at one edge of the cavity, suggesting that this black hole is actively accreting. MUSE spectroscopy reveals that this source is a low-ionization nuclear emission-line region active galactic nucleus (AGN) and that there is a second candidate AGN on the opposite side of the cavity with a relative velocity of 370 km s⁻¹—if real, this implies the presence of a kiloparsec-separation dual AGN with a total binary mass of 6 ± 2 × 10¹⁰ M_⊙, which would make this the most massive binary black hole system discovered to date. We propose that this unique stellar cavity is the result of a short-lived dynamical interaction between at least one supermassive black hole and the background stellar density field, caused either by three-body scattering during binary hardening or the induction of a dipole instability in the stellar density field.

The Orbital Architecture and Origins of the Young, Planetary-mass Companion Host System, ROXs 42B

First Author: Inglis, Julie
Instruments: SPHERE
ProgramIDs: 098.C-0864
BibCode: 2026AJ....171..280I

Understanding the origins of massive, widely separated planetary-mass companions has been an ongoing effort in the field. A subset of these objects has been found around binary stars, which can provide additional constraints on their formation histories. In this paper, we use two decades of astrometric monitoring to obtain an orbital solution for one such system, ROXs 42B, which consists of a young, ∼6−14 M_J companion orbiting a moderate (∼10 au) separation binary. We find two degenerate solutions for the mutual inclination between the binary and companion, corresponding to either a prograde or retrograde orbit, of 51° −14+24 and 130° −22+16 , respectively. Importantly, we are able to rule out scenarios in which the orbits are well aligned. We use numerical modeling to test if planet─planet scattering by multiple giant companions can reproduce the observed configuration of this system. Our observations are equally well matched by scenarios in which the companion formed in a large misaligned disk near its current semimajor axis, and those in which it was scattered outward from a smaller orbital semimajor axis via dynamical interactions with either the host binary or other planetary-mass companions. We find that capture is insufficient to explain this system given the observed stellar densities in the cluster and the age of the system. We conclude that the companion, ROXs 42B b, likely formed in the circumbinary disk.

A Salpeter IMF and an NFW halo: disentangling the dark and stellar mass of an elliptical galaxy through precise lens modelling of a double-source-plane system

First Author: Li, Tian
Instruments: MUSE
ProgramIDs: 0102.A-0950
BibCode: 2026MNRAS.548ag683L

We present a strong lensing analysis of the double source plane lens J0946+1006 (colloquially 'Jackpot' lens) to measure the inner dark matter density profile, the stellar-to-halo mass ratio, and the stellar initial mass function normalization using a two-component stellar plus dark matter mass model. The stellar mass follows a multi-Gaussian expansion light model with a free global mass-to-light ratio and an allowed radial

$M/L$

gradient, while the dark matter is described by an elliptical generalized NFW halo. The double-source-plane geometry provides additional leverage against the mass-sheet transformation and helps constrain the radial mass profile. Despite allowing both a radial stellar

$M/L$

gradient and a generalized NFW halo, the data prefer an approximately constant stellar mass-to-light ratio with a Salpeter-like IMF normalization, and a dark matter halo consistent with NFW. We infer

$M_{\star } = 4.4^{+0.25}_{-0.39}\times 10^{11}\, {\rm M}_{\odot }$

and an inner halo slope

$\gamma _{\rm in}^{\rm halo} = 1.04^{+0.10}_{-0.14}$

. The halo mass is

$M_{200}^{\rm halo} = 1.11^{+0.37}_{-0.32}\times 10^{13}\, {\rm M}_{\odot }$

, implying

$\log _{10}(M_{200}/M_{\star })=1.41^{+0.13}_{-0.14}$

. At fixed halo mass, the inferred stellar mass lies

$\sim 0.1$

dex above typical literature stellar halo mass relations at similar redshift, which is comparable to the intrinsic scatter of these relations. We expect this approach to provide a practical template for future dark matter studies with the large double-source-plane lens samples from Euclid.

The complex inner disk of the Herbig Ae star HD 100453 with VLTI/MATISSE

First Author: van Haastere, L. N. A.
Instruments: GRAVITY, MATISSE, PIONIER
ProgramIDs: 110.2474, 106.21JR, 106.21Q8, 108.225V, 0103.D-0153, 190.C-0963
BibCode: 2026A&A...708A.256V

Context. The inner regions of planet-forming disks hold invaluable insights for our understanding of planet formation. The inner disk regions that might be affected by already formed planets are of particular interest. The disk around the Herbig star HD 100453 presents one such environment, with an inner disk that is significantly misaligned with respect to the outer disk. Aims. This paper expands the existing H band (PIONIER) and K band (GRAVITY) interferometric studies of the inner disk of HD 100453 to the L band with the MATISSE VLTI instrument. Based on snapshot data spanning approximately four years, we aim to understand the inner disk structures and their potential time evolution better. Methods. Based on the MATISSE data we obtained, we used a combination of analytical models and image reconstruction to constrain the disk structure. Additionally, we fitted a temperature gradient model to the selected wavelength range of PIONIER, GRAVITY, and MATISSE to derive the physical properties of the inner regions. Results. Our parametric model determined an inclination of ≍47.5° and a position angle of ≍83.6°, which corroborates the strong misalignment of the inner to the outer disk. From the symmetric temperature gradient, we derive an inner disk radius of ≍0.27 au, with dust surface densities of Σ_subl ≍ 10^−3.2 g/cm² and a vertical optical depth τ_z,subl ≍ 0.1-0.06. Same-night MATISSE and GRAVITY observations show directional discrepancies that are inconsistent with a first-order azimuthally modulation ring. This indicates that higher-order asymmetries are required to explain the interferometric signals. This interpretation is further supported by a MATISSE snapshot image reconstruction that revealed a two-component asymmetric structure. Conclusions. The chromatic interferometric data reveal that higher-order asymmetries are probably required to explain the inner disk of HD 100453, which suggests a possible origin in dynamic interactions or disk instabilities. Coordinated multi-wavelength infrared interferometric observations with GRAVITY and MATISSE will be crucial to confirm these findings and uncover their underlying nature.

Precise measurement of WASP-31 b's Rossiter-McLaughlin effect and characterization of the planet transmission spectra

First Author: Steiner, M.
Instruments: ESPRESSO
ProgramIDs: 110.24CD, 108.2254
BibCode: 2026A&A...708A.269S

Context. Hot Jupiters are ideal natural laboratories to investigate atmospheric composition and dynamics. However, high-resolution transmission spectroscopy is currently limited by our capability of removing planet-occulted line-distortion (POLD) contamination from the signal. Aims. In this paper, we aim to characterize the transmission spectrum of WASP-31 b from two and a half transits observed with the ESPRESSO spectrograph at the VLT. Methods. The Rossiter-McLaughlin (RM) signature was analyzed using the RM "revolutions" method. Before extracting the transmission spectrum of the planet, we corrected the dataset for telluric lines using molecfit and further modeled the POLD deformations using EvE. Results. We confirm the planet low sky-projected spin-orbit angle from previous studies and further refine its value to λ = −0.09_−0.32^+0.31 deg. We do not detect any species (including previously detected species such as K or CrH) in the planetary atmosphere. In most cases the non-detections are due to the strong POLDs contamination or lack of observable lines in the ESPRESSO wavelength range, and so previous detections cannot be ruled out. Conclusions. Planet-occulted line-distortion contamination continues to be the main limitation of high-resolution transmission spectroscopy for species present in both the star and the planet, hindering atmospheric detections even with state-of-the-art models, in particular for planets with a low sky-projected spin-orbit angle. Developing advanced techniques to isolate planetary signatures is of utmost importance in the advent of ELT-like observations.

Detection of C₃ in Titan with VLT-ESPRESSO

First Author: Rianço-Silva, R.
Instruments: ESPRESSO
ProgramIDs: 114.277N
BibCode: 2026MNRAS.548ag447R

Titan is regarded as a Solar system natural laboratory for studying atmospheric photochemistry and abiotic production of organic molecules on cold small exoplanets. Since the Cassini-Huygens mission ended, telescope observations enabled new detections of increasingly complex carbon-based molecules at infrared and sub-mm wavelengths, while the optical regime has been largely overlooked. Following a recent tentative detection of the 4050 Å absorption band of C

$_3$

in Titan ─ a photochemical precursor to aromatic chemistry ─ in archived optical VLT-UVES spectra (R

$\approx$

60 000), this work presents a 8

$\sigma$

detection of the C

$_3$

4050 Å absorption band in Titan from dedicated ultra-high-resolution VLT-ESPRESSO observations of Titan (R

$\approx$

190 000, highest spectral resolution observations of Titan in optical wavelengths ever). VLT-ESPRESSO spectrum is compared to a model spectrum of Titan, for varying C

$_3$

abundances; a

$\chi ^2$

curve is drawn to assess the agreement of non-solar spectral features with C

$_3$

absorption when varying C

$_3$

abundance; and a Bayesian Markov chain Monte Carlo (MCMC) fit between model and observed spectra is performed.

$\chi ^2$

curve analysis yields an 8

$\sigma$

$_3$

detection, consistent with a C

$_3$

column density of

$N = 1.5 \times 10^{13}$

$^{-2}$

, whereas the MCMC fit retrieved a C

$_3$

column density on Titan's atmosphere of

$N = (1.47 \pm 0.30) \times 10^{13}$

$^{-2}$

at 5

$\sigma$

, the same order of magnitude of predicted C

$_3$

abundances by photochemical models, reaching ppm levels on Titan's mesosphere. This work showcases the usefulness of instruments and techniques originally dedicated to exoplanet research when applied to Solar system targets and science cases.

Chemical composition of eight OB-type stars in the local Galactic environment

First Author: Unal, Kubra Ozge
Instruments: UVES
ProgramIDs: DataDoiProID
BibCode: 2026MNRAS.548ag339U

We perform a non-local thermodynamic equilibrium spectroscopic analysis of eight OB-type stars in the solar neighbourhood, using high-resolution spectra obtained with the 0.8-m telescope at Ankara University Kreiken Observatory together with archival European Southern Observatory/Ultraviolet and Visual Echelle Spectrograph data. Stellar parameters were determined from hydrogen Balmer lines, silicon ionization equilibria, and helium line profiles, while chemical abundances were derived for He, C, N, O, Ne, Mg, Al, Si, S, and Fe. HD 37032 is newly identified as a He-rich peculiar star ([He/H]

$\approx +0.33$

dex), with asymmetric H

$\alpha$

and [O I]

$\lambda$

5577 features revealing the presence of circumstellar material. HD 46660, HD 46883, and HD 7694 likewise exhibit mild helium enrichment relative to the solar abundance. HD 29309 is found to be a double-lined spectroscopic binary hosting a Barium-star secondary. A Hertzsprung─Russell diagram analysis indicates that most of the stars are located close to the main sequence, whereas HD 46883 is classified as a blue supergiant with no strong signatures of CNO mixing. These findings provide new constraints of the chemical diversity and evolutionary pathways of early-type stars in the local Galactic environment.

SN 2023taz: Implications for the UV Diversity of Superluminous Supernovae

First Author: Aamer, Aysha
Instruments: EFOSC2, XSHOOTER
ProgramIDs: 114.27AG, 112.25JQ
BibCode: 2026ApJ..1001..181A

Superluminous supernovae (SLSNe) are some of the brightest explosions in the Universe, representing the extremes of stellar deaths. At the upper end of their distribution is SN 2023taz, in a dwarf galaxy at z = 0.407. This is one of the most luminous SLSNe discovered to date with a peak absolute magnitude of M_g,peak = ─22.75 ± 0.03 and a lower limit for energy radiated of E = 2.9 × 10⁵¹ erg. Magnetar model fits reveal individual parameter values typical of the SLSN population, but the combination of a low B-field and ejecta mass with a short spin period places SN 2023taz in a unusual region of parameter space, accounting for its extreme luminosity. The optical data around peak are consistent with a temperature of ∼17,000 K but SN 2023taz shows a surprising deficit in the UV compared to other events in this temperature range. We find no indication of dust extinction that could plausibly explain the UV deficit. The lower level of UV flux is reminiscent of the absorption seen in lower-luminosity events like SN 2017dwh, where Fe-group elements are responsible for the effect. However, in the case of SN 2023taz, there is no evidence for a larger amount of Fe-group elements which could contribute to line blanketing. Comparing to SLSNe with well-observed UV spectra, an underlying temperature of 8000─9000 K would match the UV spectral slope, but is not consistent with the optical color temperatures of these events. The most likely explanation is enhanced absorption by intermediate-mass elements, challenging previous findings that SLSNe exhibit similar UV absorption line equivalent widths. This highlights the need for expanded UV spectroscopic coverage of SLSNe, especially at early times, to build a framework for interpreting their diversity and to enable classification at higher redshifts where optical observations will exclusively probe rest-frame UV emission.

AVID: A near-major post-merger of late-type dwarfs beneath a regularly rotating H I disk (VCC 693)

First Author: Li, Fujia
Instruments: MUSE
ProgramIDs: 098.A-0364
BibCode: 2026A&A...708A.233L

In the periphery of galaxy clusters, the combination of moderately high galaxy number densities and modest velocity dispersions favors interactions and mergers that affect the galaxy evolution prior to cluster infall. Observational studies of this important phase of galaxy evolution, particularly in the dwarf galaxy regime, are still rare. We present a high-resolution case study of VCC 693 (stellar mass ∼ 2.8 × 10⁸ M_⊙), a merger remnant in the outskirts of the Virgo cluster, using observations from the project Atomic gas in Virgo Interacting Dwarf galaxies (AVID). We explored the consequences of the merger on the star formation and structural evolution of VCC 693, based on a joint analysis of high-resolution Karl G. Jansky Very Large Array and high-sensitivity Five-Hundred-meter Aperture Spherical radio Telescope H I emission line observations, optical broadband images, narrowband Hα images, and optical spectra. We also employed hydrodynamical simulations of dwarf-dwarf mergers to aid in interpreting the observations of VCC 693. Our analysis favors a near-major merger between two late-type dwarf galaxies with a stellar mass ratio of approximately 3:1─4:1, in which one of the progenitors is likely relatively gas poor (i.e., a damp merger). The optical appearance of VCC 693 is dominated by complex tidal structures spanning the whole system, whereas the H I gas has settled to a regular rotating disk with a normal surface density profile. Compared to dwarfs of similar mass, the star formation and gas-phase metallicity are moderately enhanced in the center. The global star formation rate, H I gas content, and H I-to-optical size ratio of VCC 693 are broadly consistent with those of typical late-type dwarfs of similar mass, although they fall at the lower side of the distributions. By decomposing the H I rotation curve into the baryonic and dark matter component, we found that the dark matter halo is characterized by an unusually high concentration or core density. This implies that the dark matter halo might have relaxed into a more centrally peaked distribution following the merger event. Together with two other recent studies of AVID post-merger systems, our findings reinforce the emerging view that even major mergers between dwarfs can produce remnants whose overall stellar structures, apart from tidal features, are indistinguishable from those of ordinary dwarfs, and that the diverse environmental effects experienced by galaxies in cluster outskirts can promote damp or mixed mergers, which constitute an integral part of galactic preprocessing.

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