Latest ESO telbib papers

pop-cosmos: redshifts and physical properties of KiDS-1000 galaxies

First Author: Halder, Anik
Instruments: OMEGACAM, VIRCAM
ProgramIDs: 179.A-2004, 177.A-3016, 177.A-3017, 177.A-3018
BibCode: 2026MNRAS.551g1590H

Principled Bayesian inference of galaxy properties has not previously been performed for wide-area weak-lensing surveys with millions of sources. We address this gap by applying the pop-cosmos generative model to perform spectral energy distribution (SED) fitting for 4 million KiDS (Kilo-Degree Survey)-1000 galaxies. Calibrated on deep COSMOS2020 photometric data, pop-cosmos specifies a physically motivated prior over the galaxy population up to

$z \simeq 6$

in stellar population synthesis (SPS) parameter space. Using the Speculator SPS emulator with GPU (graphics processing unit)-accelerated Markov Chain Monte Carlo sampling, we perform full posterior inference at 8.2 GPU seconds per galaxy, obtaining joint constraints on galaxy redshifts and physical properties. We validate photometric redshifts against

$\sim \!185\,\!000$

KiDS galaxies cross-matched to Dark Energy Spectroscopic Instrument Data Release 1 spectroscopic samples, achieving low bias (

$2\times 10^{-3}$

), scatter (

$\sigma _{\mathrm{MAD}}=0.03$

), and outlier fraction (3.2 per cent) for the Bright Galaxy Survey, with comparable performance (bias

$3\times 10^{-2}$

$\sigma _{\mathrm{MAD}}=0.05$

, 1.0 per cent outliers) for luminous red galaxies (LRGs). Within the LRG sample, we identify massive, dusty, star-forming contaminants at

$z \simeq 0.4$

satisfying standard colour selections for quenched populations. We infer trends in stellar mass, star formation, metallicity, and dust across five tomographic redshift bins consistent with established scaling relations. Using specific star formation rate constraints, we identify

$\sim$

7 per cent of KiDS-1000 galaxies as quenched, versus 37 per cent implied by conservative colour cuts. This enables the construction of weak-lensing samples defined by physical properties while mitigating intrinsic alignment systematics and preserving statistical power. Our analysis validates pop-cosmos out of sample, establishing it as a scalable approach for galaxy evolution and cosmological analyses with photometric surveys.

The SAMI galaxy survey: linking tidal features and orbit populations using Schwarzschild modelling

First Author: Rutherford, T. H.
Instruments: OMEGACAM, VIRCAM
ProgramIDs: 179.A-2004, 177.A-3018, 177.A-3016, 177.A-3017
BibCode: 2026MNRAS.551g1540R

The evolution of angular momentum in galaxies is shaped by a combination of internal secular processes and external mechanisms such as mergers. Orbit-superposition based dynamical modelling provides a powerful means of linking the intrinsic orbital structures of galaxies to their global properties and merger histories. We construct Schwarzschild orbit-superposition models of massive (

$\log _{10}\!\left(\rm {M}_*/\rm {M}_\odot \right)$

>10) SAMI galaxies using the DYNAMITE code, utilising deep Kilo-Degree Survey photometry to accurately reproduce each galaxy's luminosity distribution. We find that the fractions of hot, cold, warm, and counter-rotating orbits all show significant correlations with the spin parameter proxy

$\lambda _{R_{\rm {e}}}$

, with the strongest correlation arising from the combined hot plus counter-rotating fraction. When controlling for stellar mass and environment, we find that the fraction of hot and cold orbits show significant correlations with stellar age, whereas warm orbits do not. We further find that the lower values of

$\lambda _{R_{\rm {e}}}$

for young galaxies with shell merger features as compared to the full sample is driven by an excess of hot orbits and a deficit of cold orbits, with no dependence on warm orbits. We suggest that the kinematic transformation in this SAMI sample proceeds through stars transitioning directly from cold to hot orbits. As warm orbits are expected to arise from secular heating processes, these findings indicate that merger-driven heating is the dominant mechanism governing the redistribution of angular momentum and the reduction of rotational support in massive galaxies.

The ALMA survey to Resolve exoKuiper belt Substructures (ARKS): III. The vertical structure of debris disks

First Author: Zawadzki, B.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2012.1.00142.S, 2012.1.00198.S, 2015.1.01260.S, 2016.1.00104.S, 2016.1.00195.S, 2016.1.00907.S, 2017.1.00167.S, 2017.1.00825.S, 2018.1.01222.S, 2019.1.00189.S, 2022.1.00338.L
BibCode: 2026A&A...705A.197Z

Context. Debris disks ─ collisionally sustained belts of dust and sometimes gas around main sequence stars ─ are remnants of planet formation processes and are found in systems ≳10 Myr old. Millimeter-wavelength observations are particularly important, as the grains probed by these observations are not strongly affected by radiation pressure and stellar winds, allowing them to probe the dynamics of large bodies producing dust. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is analyzing high-resolution observations of 24 debris disks to enable the characterization of debris disk substructures across a large sample for the first time. Aims. For the most highly inclined disks, it is possible to recover the vertical structure of the disk. We aim to model and analyze the most highly inclined systems in the ARKS sample in order to uniformly extract the vertical dust distributions for a sample of well-resolved debris disks. Methods. We employed both parametric and nonparametric methods to constrain the vertical dust distributions for the most highly inclined ARKS targets. Results. We find a broad range of aspect ratios, revealing a wide diversity in vertical structure, with a range of best-fit parametric values of 0.0026 ≤ h_HWHM ≤ 0.193 and a median best-fit value of h_HWHM = 0.021. The results obtained by nonparametric modeling are generally consistent with the parametric modeling results. We find that five of the 13 disks are consistent with having total disk masses less than that of Neptune (17 M_⊕), assuming stirring by internal processes (self-stirring and collisional and frictional damping). Furthermore, most systems show a significant preference for a Lorentzian vertical profile rather than a Gaussian.

Forecasting the Observable Rates of Gravitationally Lensed Supernovae for the PASSAGES Dusty Starbursts

First Author: Kamieneski, Patrick S.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2015.1.01518.S, 2016.1.00048.S, 2017.1.01214.S, 2019.1.01636.S
BibCode: 2026ApJ..1000..235K

More than 60 years have passed since the first formal suggestion to use strongly lensed supernovae (SNe) to measure the expansion rate of the Universe through time-delay cosmography. Yet, fewer than 10 such objects have ever been discovered. We consider the merits of a targeted strategy focused on lensed hyperluminous infrared galaxies, which are among the most rapidly star-forming galaxies known in the Universe. With star formation rates (SFRs) ∼200─6000 M_⊙ yr⁻¹, the ∼30 objects in the Planck All-Sky Survey to Analyze Gravitationally-lensed Extreme Starbursts are excellent candidates for a case study, in particular, and have already led to the discovery of the multiply imaged SN H0pe. Considering their lens model-corrected SFRs, we estimate their intrinsic SN rates to be an extraordinary 1.8─65 yr⁻¹ (core-collapse) and 0.2─6.4 yr⁻¹ (Type Ia). Moreover, these massive starbursts typically have star-forming companions which are unaccounted for in this tally. We demonstrate a strong correlation between Einstein radius and typical time delays, with cluster lenses often exceeding several months (and therefore most favorable for high-precision H₀ inferences). A multivisit monitoring campaign with a sensitive infrared telescope (namely, JWST) is necessary to mitigate dust attenuation. Nevertheless, a porous interstellar medium and clumpy star formation in these extreme galaxies might produce favorable conditions for detecting SNe as transient point sources. Targeted campaigns of known lensed galaxies to discover new lensed SNe can greatly complement wide-area cadenced surveys. Increasing the sample size helps to realize the potential of SN time-delay cosmography to elucidate the Hubble tension through a single-step measurement, independent of other H₀ techniques.

JOYS+: A JWST/MIRI survey of the evolution of H₂ winds and jets from low-mass protostars

First Author: Francis, L.
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2013.1.00031.S, 2013.1.00726.S, 2017.1.00053.S, 2017.1.01078.S, 2017.1.01350.S, 2018.1.00701.S, 2019.1.00261.L, 2019.A.00034.S, 2021.1.00418.S, 2021.1.01578.S
BibCode: 2026A&A...711A.258F

Context. The base of protostellar outflows can display both wide-angle, low-velocity winds and high-velocity, collimated jets, the magnetocentrifugal launching of which enables accretion onto the protostar. In outflows from the youngest protostars, the majority of the ejected or entrained mass is likely molecular H₂ . How the H₂ outflow evolves as the central protostar grows and the envelope dissipates is important for understanding the nature of the launching mechanism and assembly of the nascent protostar. Aims. Using JWST MIRI/MRS observations with an unprecedented spatial resolution down to 0.3" towards 13 single and 20 multiple Class 0 and I protostars, we aim to investigate the H₂ wind and jet morphology, mass outflow rate, velocity and temperature structure, and the evolution of these properties with protostellar class. Methods. We constructed continuum-subtracted maps of the H₂ S(1) and S(7) line flux and velocity towards the outflows in our sample and ALMA sub-millimetre CO maps. Towards the base of each blueshifted outflow lobe (typically within 300 au), we extracted representative spectra and measured the outflow opening angles from the H₂ S(1) line emission. A rotation-diagram fitting of the H₂ lines was used to determine the column density and temperature, which was combined with measurements of the outflow width and H₂ line velocity to measure the mass-loss rates. Results. Low- J (J ≤ 4) transitions of H₂ largely trace extended wide-angle, low-velocity (0-20 km s⁻¹) winds within the contours of the low-velocity (<30 km s⁻¹) sub-millimetre CO emission, while high-J (J > 5) transitions are associated with shocks and knots. In Class 0 sources with a known high-velocity (>30 km s⁻¹) molecular CO or SiO jet, higher H₂ velocities are observed along the jet axis. The opening angle of the wind traced by the H₂ S(1) line broadens from ∼20° to ∼90° through the Class 0 to the Class I stage. The rotation diagrams in the blueshifted outflow lobes show a clear separation between a warm, ∼600 K and a hot, 1500-3000 K component, with no clear sign of evolution in the excitation temperature. The warm component contains two orders of magnitude more mass than the hot component, and the H₂ outflow mass-loss rate declines by two orders of magnitude from the Class 0 to the Class II stage. A correlation with the bolometric luminosity of the driving source is observed. A factor of 10─1000 mismatch between the warm H₂ and cold sub-millimetre CO outflow rate and momentum flux is also seen, which is consistent with the presence of cold and likely entrained (<150 K) molecular H₂ that cannot be detected with JWST/MIRI. Conclusions. The declining warm H₂ mass-loss rates and increasing opening angles from the Class 0 to I stages ─ and the absence of H₂ jets in the Class I sources ─ are consistent with the predictions of magnetohydrodynamical (MHD) disc wind models; however, the relatively constant temperatures of the warm and hot components with evolutionary stage may reflect the typical conditions in the outflow shocks rather than temperature stratification of the wind.

The most extreme high-z radio quasars in the eRASS:1 X-ray survey

First Author: Ighina, L.
Instruments: EFOSC2
ProgramIDs: 115.28BJ
BibCode: 2026MNRAS.551g1518I

We present the selection and identification of high-z radio quasars from a combination of X-ray (eROSITA All-Sky Survey), optical/NIR (DECam Local Volume Exploration), and radio (Rapid ASKAP Continuum Survey) surveys. After building a sample of 68 new high-z quasar candidates, we performed follow-up spectroscopic observations on 46 sources, confirming 39 to have redshifts

$z\gt 3.5$

. For the subset of radio quasars at

$z\gt 4$

, the 14 new sources identified here represent an increase of

${\sim} 65$

% in the known population of objects above the same flux limits in the same area. Using X-ray-to-optical relative intensity, we identified blazars in our sample, which we then used to compare the total number of

$z\gt 4$

, X-ray selected blazars to the predictions of a fractional IC/CMB model previously proposed in the literature. Overall we find a relatively good agreement, even considering the potential biases in the redshift distribution from the incompleteness of the spectroscopic follow-up and the blazar classification criteria. The sources presented in this work represent a sample well suited for investigating the evolution of the most extreme systems in the early Universe, including their relativistic jets and accretion properties.

Exploration of the inner region of the system HD 142527

First Author: Tran, T. M. H.
Instruments: SPHERE
ProgramIDs: 095.C-0298, 096.C-0241, 097.C-0865, 096.C-0248, 115.28BA
BibCode: 2026A&A...713A..25T

Context. HD 142527 is a well-studied intermediate-mass T Tauri star surrounded by a transitional disk with a large dust cavity, spiral structures, and an accreting low-mass companion. Despite extensive observations, the system's inner regions remain poorly understood, particularly regarding their influence on disk morphology and planet formation. Aims. This study aims to investigate the inner region of HD 142527 (separation <50 au) with high detection sensitivity thanks to dedicated post-processing methods to search for undetected components and explore their potential role affecting the disk's structure and evolution. Methods. We analyze high-contrast imaging data obtained with the SPHERE instrument at the Very Large Telescope (VLT). To enhance detection sensitivity, we applied the PACO and REXPACO algorithms, dedicated respectively to the detection of point-like sources and to the reconstruction of circumstellar disks with high reliability, while exploiting both angular and spectral variations. Results. We revisit the known companion HD 142527 B and update its photometry, astrometry, and accretion rate estimates. Furthermore, we identify a new candidate companion (CC) at an angular separation of ρ ~ 0.09″ (~14 au). Though it is shown as a point-like object, the possibility that CC is a disk feature remains. Otherwise, it could be a young gas-giant planet or a brown dwarf with a mass of 12--50 M_Jup. Additionally, we report the discovery of a tightly wound Hα spiral feature in the inner disk, reconstructed for the first time by high contrast imaging. The spiral implies varying accretion dynamically linked to the known companion B and possibly to CC, suggesting ongoing interactions that influence the disk's structure. Conclusions. Our findings provide new insights into the complex interactions within the HD 142527 system, highlighting the role of multiple companions in driving disk asymmetries and facilitating planet formation. Future high-resolution observations and dynamical modeling will be essential to fully understand the system's architecture and evolution.

VLT/MUSE Study of Close Active Galactic Nucleus Pairs and Host Galaxies in the Local Universe. I. Overview of the Ionized Gas

First Author: Xu, Xiaoyu
Instruments: MUSE
ProgramIDs: 0103.A-0637, 095.B-0482, 109.238W, 110.23WR, 0101.D-0748, 0100.B-0116
BibCode: 2026ApJS..286...30X

Studying active galactic nucleus (AGN) pairs and their host galaxies is essential for understanding the interplay between galaxy mergers and key internal processes such as supermassive black hole fueling and feedback. We crossmatch between the Big Multi-AGN Catalog and the public data archive of the Very Large Telescope (VLT)/MUSE, and obtain 12 AGN pair candidates in the local Universe (z ≲ 0.1) with a projected distance of r_p <= 20 kpc. Using archival VLT/MUSE data, we present a spatially resolved study of the ionized gas kinematics and ionization properties of these 12 AGN pair candidates. By decomposing the optical emission lines into two Gaussian components, we try to separate gas associated with disk rotation from noncircular motions. We further identify dominant ionization mechanisms using spatially resolved Baldwin--Phillips--Terlevich diagnostics. We find that both nuclei in four of the 12 systems are classified as a Seyfert or LINER. In addition, three nuclei are classified as star-forming or composite in the optical diagnostics, but are identified as AGNs at other wavelengths. Kinematically, regularly rotating ionized gas disks are detected in 16 of 24 nuclei. Prominent tidal features traced by ionized gas are also detected in nine systems. Ionized gas outflows are widespread and are detected in 18 nuclei. Finally, for three nuclei (Mrk 739A, NGC 7592B, and J1544+0446A), we find evidence for fading AGN activity over the past several tens of thousands of years, based on optical emission-line ratios and an assumed AGN photoionization model.

ALMA High-J CO Spectroscopy of High-redshift Galaxies. II. 0 .″ 03 Resolution CO Kinematics Reveal S

First Author: Tadaki, Ken-ichi
Instruments: ALMA_Band_5, ALMA_Band_7
ProgramIDs: 2021.1.00168.S, 2022.1.00353.S, 2024.1.01175.S
BibCode: 2026ApJ..1006..117T

We present ultrahigh-resolution ( 0.″03≍230 pc) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the hyperluminous dust-obscured galaxy W2305−0039 at z = 3.111, targeting the CO J = 7─6 and J = 11─10 lines. The CO (11─10) emission is extremely compact and exhibits anomalously high excitation relative to CO (7─6) within the central ≲500 pc. X-ray-dominated region models successfully reproduce this excitation, providing strong evidence for intense X-ray irradiation by a deeply obscured active galactic nucleus (AGN), while photodissociation region models fail to match the observed ratio. Forward modeling of the nuclear CO(11─10) position─velocity diagram yields a dynamical black hole mass of log(MBH/M⊙)=8.3−0.6+0.7 and an intrinsic gas velocity dispersion of σgas=277−14+16 km s⁻¹. Combined with the AGN luminosity from infrared spectral energy distribution decomposition, these measurements imply a highly super-Eddington accretion state with λ_Edd ≳ 4. Our results provide dynamical evidence that the most rapid phases of black hole growth can occur within a compact, heavily obscured nuclear region. Extending ALMA beyond its current 16 km maximum baselines will be essential for pushing such dynamical measurements to tens-of-parsec scales and resolving the black hole sphere of influence in massive galaxies at z ≳ 6.

Three new exoplanet systems from the Dispersed Matter Planet Project

First Author: Barnes, J. R.
Instruments: ESPRESSO, HARPS
ProgramIDs: 098.C-0269, 0100.C-0836, 114.27LM, 099.C-0798, 095.C-0799, 097.C-0390, 110.248C
BibCode: 2026MNRAS.551g1486B

We present a radial velocity analysis of three bright, low-activity stars identified by the Dispersed Matter Planet Project (DMPP). We use a Bayesian framework to compare purely Keplerian models with models incorporating stellar activity via a quasi-periodic Gaussian Process (GP). DMPP-7 (HD 118006) is a slightly evolved star that harbours a single 0.72 Saturn-mass giant (

$m_\rm {p}\, \sin \, i$

$= 69$

$_{\oplus }$

) with an orbital period of

$P=4.93$

d. A longer 21 -- 22 d period cannot be conclusively confirmed as a stellar rotation signature rather than a purely Keplerian signal. For HD 67200, which exhibits Ca II H&K variability, a model with only a GP is strongly favoured over a purely dynamical model. The GP model shows moderate evidence for a single Keplerian with

$P=2.67$

d. For HD 2134, a 21 -- 32 d rotation period signal is associated with tentative Full Width at Half Maximum variability. A model with a GP is not conclusively favoured, but all models considered show moderate evidence for an additional single Keplerian with

$P=2.78$

d. Despite our target selection favouring near edge-on orbital geometries, we find no evidence for transits in Transiting Exoplanet Survey Satellite photometry. DMPP-7 b lies at the transition between the high-radius population and the Neptunian ridge and savannah regions. Further observations are required to establish whether the coherent short-period HD 67200 and HD 2134 signals are stellar or dynamical in origin. If planetary, the signals correspond to minimum masses of

$m_\rm {p}\, \sin \, i$

$= 2.07$

$_{\oplus }$

and

$m_\rm {p}\, \sin \, i$

$= 2.86$

$_{\oplus }$

The Exceptional 2017 γ-Ray Flare of the Radio Galaxy NGC 1275: VERITAS and Multiwavelength Observations

First Author: Acharyya, A.
Instruments: ALMA_Band_3, ALMA_Band_5, ALMA_Band_6, ALMA_Band_7, ALMA_Band_9
ProgramIDs: 2012.1.00394.S, 2016.1.01305.S, 2017.1.01257.S, 2018.1.01438.S
BibCode: 2026ApJ..1006...12A

The radio galaxy NGC 1275 is the brightest cluster galaxy in the Perseus Cluster. It is well studied across all wave bands, including very high-energy (VHE; E ≥ 100 GeV) γ-rays, and with radio observations over the last 20 yr tracking an unusual radio component, "C3." NGC 1275 was observed in an exceptional VHE-flaring state between 2016 December 31 and 2017 January 3. The flare peak reached ∼1.5 Crab units as measured by the MAGIC observatory. We report on the observations of NGC 1275 conducted by VERITAS and multiwavelength data collected during this flaring state and, for context, data taken between 2009 and 2017 inclusively. VERITAS detected the declining state of the flare on 2017 January 2 (MJD 57755) and 3 (MJD 57756) at an average flux state of 0.5 Crab units. VERITAS spectra show an overall long-term trend of harder when brighter. During the flare, the γ-ray spectrum obtained from the combined Fermi-LAT, MAGIC, and VERITAS observations changes from a power law with an exponential cutoff on January 1 to a log-parabola on January 2. To study the evolution of the flare in more detail, multiband spectral energy distributions (SEDs) were constructed for the nights of 2017 January 1 and 2 corresponding to the shift from the peak to the decline of the flare. A blob-in-jet modeling of the SEDs results in support for a two-component model with a θ = 10^∘ jet angle to the line of sight and the γ-ray emission zone located in the vicinity of the C3 radio component.

A closer look at the WISPIT 2 host star: Evidence of a spectroscopic binary

First Author: Burgy, C. J.
Instruments: XSHOOTER
ProgramIDs: 116.2ASZ
BibCode: 2026A&A...713L...1B

Context. While hundreds of protoplanetary discs have been studied in great detail, the detection of protoplanets that are still embedded in their native discs remains rare. WISPIT 2 is only the second laboratory allowing us to directly study planet formation while in progress. The recently discovered system hosts two giant protoplanets in a multi-ringed disc. Aims. We characterise the WISPIT 2 host star spectroscopically to determine its stellar properties, accretion rate, and inner disc diagnostics to provide a more complete picture of the system. Methods. We present optical and near-infrared spectroscopic observations obtained with the ESO VLT/X-shooter and 2.2 m/FEROS instruments. We modelled the stellar spectrum to determine the spectral type and effective temperature, analysed the emission lines to estimate the accretion rate, and searched for evidence of a close stellar companion using radial velocity measurements. Results. Our observations reveal that WISPIT 2 is a spectroscopic binary. The binary has a period of (4.8 ± 0.1) days, which corresponds to a semi-major axis of 0.072 au or 15.54 R_⊙, assuming co-planarity with the disc and a circular orbit. The binary system consists of a ~0.97 M_⊙ primary of spectral type K3 (T_eff ~ 4700 K) and a ~0.33 M_⊙ secondary (mass ratio ~0.34). We detect weak Hα emission below the typical chromospheric level, indicating little to no ongoing accretion onto the young stars, consistent with an accretion rate of ≲2 × 10^-11 M_⊙ yr^-1. Conclusions. This discovery makes the WISPIT 2 disc the first circumbinary system with directly imaged protoplanets and establishes this system as a unique benchmark for studying planet formation and disc evolution around binary stars.

Discovery of a low-surface-brightness galaxy in the Zone of Avoidance using VVVX Deepstack imaging

First Author: Nilo-Castellon, J. L.
Instruments: VIRCAM
ProgramIDs: 179.B-2002, 198.B-2004
BibCode: 2026A&A...713L...3N

We report the discovery of VVVX J080705.96-273823.6, the first low-surface-brightness galaxy candidate identified in the Zone of Avoidance by the VISTA Variables in the Vía Láctea eXtended Survey (VVVX). The source was detected serendipitously during a visual inspection of the new Deepstack images, a set of reconstructed mosaics generated through an updated reprocessing. The associated stacking procedure that significantly improves both the depth and spatial uniformity of the original survey images. First-order morpho-photometric parameters were obtained using SExtractor in combination with PSF models derived with PSFEx, applied to star-subtracted images to minimize foreground contamination. The final structural properties of the galaxy were derived from PSF-convolved modelling of azimuthally averaged surface-brightness profiles in the J, H, and K_s bands using exponential, Sérsic, and composite models. The galaxy candidate is clearly detected in the three available near-infrared bands. The azimuthally averaged profiles are consistently described by a disk-dominated (exponential) model in all three bands, with exponential scale lengths in the range h ~ 32--36″ and extinction-corrected central surface brightness values spanning μ₀ ≃ 19.82--22.35 mag arcsec^-2. The J band gives the best-constrained profile; H and K_s show the same behaviour with larger uncertainties. The projected proximity to the galaxies ESO 494-25 and ESO 494-26 raises the possibility of a physical association. Both ESO galaxies have radial velocities consistent with distances of ~11--12 Mpc. If VVVX J080705.96-273823.6 were located at the same distance, its characteristic exponential scale length of h ≃ 34″ would correspond to ~1.8--2.0 kpc, consistent with the range of scale lengths observed in nearby LSB disk galaxies. However, in the absence of a spectroscopic redshift, this association remains tentative. This discovery demonstrates that the new VVVX Deepstack products can reveal faint diffuse galaxies at low Galactic latitudes, opening a path toward a more complete census of the obscured nearby Universe.

3D rotation of the open cluster NGC 2516

First Author: Wright, Nicholas J.
Instruments: FLAMES, GIRAFFE, UVES
ProgramIDs: 188.B-3002
BibCode: 2026MNRAS.551g1576W

We have combined Gaia astrometry with Gaia-ESO Survey radial velocities to measure the 3D rotation of the open cluster NGC 2516. We compiled a sample of 376 members with astrometry and spectroscopy and use these to determine a distance to the cluster of

$406.4 \pm 0.8$

pc, which we then use to infer the 3D positions and velocities of all stars in the cluster using a Bayesian model. We identify the axis of maximum cluster rotation and measure a median rotational velocity of

$0.11 \pm 0.02$

km s

$^{-1}$

. We find the axis of maximum cluster rotation to be

$52^\circ \pm 22^\circ$

to the plane of our Galaxy. We compare this rotation rate to measurements of cluster rotation in other open clusters and find that it is inconsistent with the expected dependences on cluster age and mass.

Light curve and spectral properties of Type II supernovae from the ATLAS survey

First Author: Ertini, K.
Instruments: EFOSC2
ProgramIDs: 1103.D-0328, 106.216C, 108.220C
BibCode: 2026A&A...713A..29E

Context. Type II supernovae (SNe) are the most common terminal stellar explosions in the Universe. With SNe now being detected within days after first light, there is growing evidence that most Type II SNe (SNe II) show signs of interaction with a dense, confined circumstellar material (CSM) in the first few days after first light. Aims. We aim to bridge the gap between single SN studies showing early-time interaction in their spectra and statistical studies of early-time SN light curves, which imply the existence of CSM. Methods. We present a sample of 68 Type II SNe with both early photometric data obtained by the ATLAS survey and spectroscopic data obtained by the ePESSTO+ collaboration. A subset of the sample is classified based on the presence or absence of narrow spectral features with electron-scattered broadened wings in the early spectra, indicative of interaction with the CSM. We characterised the photometric and spectroscopic properties of the sample by measuring rise times to maximum light, peak magnitudes, decline rates, and line velocities. Additionally, we measured the ratio of absorption to emission (a/e) of the Hα P-Cygni profile. Results. Our analysis reveals that SNe II showing early spectroscopic signs of interaction with the CSM decline faster and are brighter than those without. However no difference was found in rise times between the two groups. A clear separation can be observed in the a/e ratio, namely, SNe with signs of interaction exhibit lower a/e ratios at all epochs compared to those without. Our results highlight that understanding SN II ejecta-CSM interaction requires large uniform samples of photometric and spectroscopic data, such as the one presented in this work.

SN 2019cqc: A Hydrogen-rich Superluminous Supernova Showing Electron-scattering Signatures

First Author: Hebbar, Dinesh
Instruments: EFOSC2
ProgramIDs: 1103.D-0328, 106.216C
BibCode: 2026ApJ..1008..135H

Hydrogen-rich superluminous supernovae without narrow emission lines (SLSNe-II) are rare transients whose powering mechanisms remain debated, particularly the role of circumstellar medium (CSM) interaction. We present photometric and spectroscopic observations of SN 2019cqc to investigate its power source and progenitor mass loss. We model the lightcurve using MOSFiT with the csm and csmni models to constrain the explosion and CSM parameters. SN 2019cqc peaked at M_g = -20.21 ± 0.07 and emitted ~1.7 × 10⁵⁰ erg of energy in the form of radiation. Photometric and spectroscopic modeling indicates that CSM interaction dominates in both scenarios, with best-fit CSM and ejecta masses of ~4.5 M_⊙and ~32 M_⊙, respectively. The inferred CSM properties imply an extreme eruptive mass loss at a rate of ~0.2--0.3 M_⊙, yr^-1 in the years preceding the core collapse, consistent with a variable progenitor of luminous blue variable progenitor. We observe a persistent blueshifted asymmetry in the Hα emission line. At early times (≲+110 days), this is attributed to electron scattering with the bulk velocity of ejecta, while the profile at late epochs (≳ +402 days onward) suggests the subsequent formation of dust in the ejecta. Additionally, we identify a distinct, short-lived feature at ~4600 Å, likely a blend of ionized C III/N III lines powered by the interaction of the SN-shock with the extended atmosphere.

exoALMA. XXIV. Formaldehyde Emission in Protoplanetary Disks of exoALMA Compared with Their Properties and Dynamical State

First Author: Alarcón, Felipe
Instruments: ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2016.1.00484.L, 2021.1.01123.L, 2022.1.00485.S, 2023.1.00334.S
BibCode: 2026ApJ..1000L..32A

The presence of asymmetries and substructures in protoplanetary disks, revealed by both dust and gas emission, highlights the potential interplay and the broader connection between chemistry and dynamics in disk evolution. We explore multiple relationships using the nonparametric Kendall-τ correlation to examine formaldehyde (H₂CO) emission with relation to stellar and disk properties for a subset of disks from the exoALMA sample. We also retrieve the H₂CO column density and excitation temperature using four transitions, measured in radial bins of 100 au, and quantify the level of asymmetry in the resolved peak intensity of the H₂CO emission. From our correlation analysis, we find no correlations with sufficient statistical significance. However, we identify tentative relationships that can be tested with larger samples. In particular, we report a proposed correlation (2.1σ) between stellar effective temperature and the formaldehyde excitation conditions, suggesting that, to first order, the central star dominates the nature of the H₂CO emission over possible dynamical asymmetries traced by dust. Although a correlation with the stellar luminosity was also expected, a larger sample is required to confirm or refute this trend. A possible correlation with spectral type, together with the broad range of H₂CO excitation temperatures within the inner 100 au of the studied disks, hint at possible multiple chemical formation pathways for H₂CO, including both gas-phase reactions and ice-surface chemistry on dust grains.

The asymmetric carbon-rich chemistry of the planet-forming disk of HD 142527 triggered by late infall

First Author: Temmink, Milou
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_7, ALMA_Band_8
ProgramIDs: 2011.0.00318.S, 2011.0.00465.S, 2012.1.00631.S, 2013.1.00305.S, 2015.1.00805.S, 2015.1.01137.S, 2023.1.00628.S, 2024.1.00446.S
BibCode: 2026A&A...711A.137T

The planet-forming disk of HD 142527 is known for its azimuthally asymmetric dust trap, shadows, and spiral arms. In this work we used new observations of the Atacama Large Millimeter/submillimeter Array to investigate the molecular composition and to determine the ongoing chemical processes and the origin of its asymmetric molecular emission, and to infer possible effects of dust continuum obscuration. The observations cover a wide variety of molecular species over a large frequency range, enlarging the known molecular inventory of this system. Strikingly, the emission of H₂CO, CN, and C₂H is dominated by spiral-like features peaking in the southern region of the disk, opposite to the large dust trap, while no relation is found between the observed asymmetries and the shadows seen in the scattered light due to the misaligned inner disk. We attribute these features to low-density, late infalling, atomic carbon-rich material that locally increases the C/O ratio and, subsequently, facilitates the gas-phase formation of these species. Azimuthal offsets between the peak emission of H₂CO and that of CN and C₂H are possibly due to a delay of a few hundred years in the gas-phase formation of H₂CO. As opposed to the emission of H₂CO, CN, and C₂H, the emission of C¹⁷O and the HCO⁺ J=1─0 transition is aligned with the large dust trap, likely due to an azimuthal increase in the surface density. Differences between the two observed C¹⁷O transitions may be due to dust obscuration effects. These effects are not expected to affect molecular emission at 3 mm, given the lower optical depth of the dust trap. The four observed transitions of CS display different azimuthal extents and strengths, with the lines with lower upper-level energies appearing more ring-like. An analysis of the ¹³CO brightness temperature yields no significant temperature variations across the disk's azimuth. Therefore, we propose that the observed CS transitions trace two different reservoirs: a cold reservoir that resides on a Keplerian orbit and a second, hotter reservoir of CS that is facilitated by the infalling material and resides in a higher atmospheric layer of the disk. A single weak transition of SO is observed, which may be explained by weak shocks induced by the spirals observed in the scattered light that liberate sulphur. Future higher-resolution, multi-line observations of species such as H₂CO, CS, CN, and C₂H are needed to investigate the role and importance of late infalling material in setting the chemical composition of planet-forming disks.

Lithium and the evolution of intermediate-mass T Tauri and Herbig stars: Rotation, accretion, and planets

First Author: Mendigutia, I.
Instruments: ESPRESSO, FLAMES, GIRAFFE, UVES, XSHOOTER
ProgramIDs: DataDoiProID, 2103.C-5025
BibCode: 2026A&A...709A.221M

Context. Interior models predict that stellar envelopes change from convective to radiative during the pre-main-sequence (pre-MS) evolution of intermediate-mass stars. Although the amount of surface lithium (Li) is a direct probe of mixing in stellar interiors, analyses focused on this type of source are practically absent. Aims. We contribute to our understanding of the evolution of young intermediate-mass stars by providing a comprehensive analysis of their Li content. Methods. A sample of 71 intermediate-mass T Tauri (IMTT) and Herbig stars within the mass range 1.5─3.5 M_⊙ was carefully selected for the analysis. Metallicities, rotational velocities, and accretion rates were obtained from spectra. The curves of growth for stars hotter than 8000 K were built to infer the Li abundances, which were interpreted considering standard models of stellar interiors and non-standard processes affecting Li depletion. Results. Li is generally less strongly depleted in intermediate-mass stars than in their lower-mass counterparts, as expected from standard evolution models. However, Li abundances significantly below the cosmic value are observed in 25─30% of intermediate-mass stars. It is also unexpected that the results show no significant difference between the 1.5─2.5 M_⊙ and 2.5─3.5 M_⊙ subsamples. Evidence is provided showing that disk-locking works in young intermediate-mass stars. This constitutes independent support for the hypothesis that magnetospheric accretion scenario operates in these sources. We found that disk-locking is effective for a timescale that is about twice shorter than for lower-mass stars, before magnetospheres reduce their sizes during the transition from the IMTT to the Herbig regime. This contraction of the magnetosphere can explain the increase in rotation by a factor of about 3 and in accretion by a factor of about 4 that is observed during this transition. We propose a complex scenario linking rotation, accretion, and the surface Li abundance. Finally, we tentatively suggest that the known relation between the presence of planets and Li depletion might also be present in intermediate-mass MS stars and might originate in the pre-MS. Conclusions. We provide the most complete Li analysis and database focused on IMTT and Herbig stars to date. However, we emphasize the need of additional observations and non-standard models such as those available for their lower-mass analogs.

Cosmic Duets: I. High-spatial resolution spectroscopy of dual and lensed active galactic nuclei with MUSE-NFM

First Author: Scialpi, M.
Instruments: EFOSC2, FORS2, MUSE
ProgramIDs: 114.27BY, 115.28CQ, 109.22W5, 114.27FC, 113.26TB, 110.23SM, 109.22W4, 112.25CT
BibCode: 2026A&A...709A.236S

We present the first-year results of the MUSE Large Program "Cosmic Duets", whose goal is to obtain adaptive-optics assisted MUSE observations with a typical angular resolution of 0.1″ − 0.2″ in order to provide integral-field spectroscopy of sub-arcsec separation dual and lensed active galactic nucleus (AGN) candidates. These observations reveal previously unexplored properties of dual and lensed systems that are key to understanding galaxy evolution, supermassive black hole mergers, and strong-lensing modeling. Targets were efficiently selected using the Gaia multipeak (GMP) technique, which identifies pairs of point-like sources with angular separations below 0.8″ in the Gaia catalog. MUSE spatially resolved spectroscopy provides accurate redshifts, ionization diagnostics, and identification of absorption systems along the line of sight. We report results for 30 GMP-selected targets at z = 0.5 − 3.5. All systems show at least two spatially resolved components. Nineteen objects are confirmed as AGN multiplets, including six dual AGN, ten doubly lensed quasars, and three quadruply lensed systems, while the remaining 11 correspond to chance alignments with foreground stars. Among all the spectroscopically confirmed dual AGN in the literature, 27 pairs have projected separations below 7 kpc in this redshift regime, and our sample accounts for 22% of the total. We studied dual and lensed AGN distributions as a function of redshift, magnitude, and projected separation while accounting for selection effects, and we find that bright systems (J ≲ 16.5) are dominated by lensed quasars, whereas the relative fraction of dual AGN increases at fainter magnitudes. This first-year sample demonstrates the high efficiency of GMP preselection combined with MUSE spectroscopy for identifying sub-arcsec dual and lensed AGN. The full program, targeting ∼150 systems, will enable statistical studies of dual AGN incidence as a function of redshift, separation, and luminosity and allow for precise characterization of the mass composition and distribution in strong lensing galaxies.

Quantitative spectroscopy of single and multiple OB-type stars: Non-LTE spectrum analysis with machine learning

First Author: Aschenbrenner, P.
Instruments: FEROS, HARPS, NIRPS, XSHOOTER
ProgramIDs: 60.A-9022, 091.C-0713, DataDoiProID
BibCode: 2026A&A...709A.124A

Aims. The plethora of spectra of OB-type stars in observatory archives and the much larger numbers to come from the WEAVE and 4MOST spectroscopic facilities require efficient, but also accurate and precise methods for (semi)automatic quantitative analyses. Methods. Neural networks were used to emulate the spectra of single- and multi-star systems, trained on hybrid non-local thermodynamic equilibrium models that cover a wide range of atmospheric parameters and chemical compositions. To derive the full set of stellar atmospheric parameters and uncertainties, a Markov chain Monte Carlo algorithm was implemented to fit high-resolution spectra within 3000─10 500 Å. Results. The neural networks and fitting algorithm were bundled into a programme called Spectral Analysis Tool Using Restricted Neural networks (SATURN). In its current implementation, SATURN facilitates the emulation of synthetic spectra for spectral types O7 to B9, which differ only negligibly from computed models. SATURN was tested on a number of benchmark stars that have been studied before, including single OB stars and a detached eclipsing binary (DEB) system. Excellent agreement of atmospheric parameters and elemental abundances for up to ten metal species is found with respect to the data in the literature, often with reduced uncertainties of about 1% in effective temperature and 0.05 dex in surface gravity (1σ values). For DEB components, the uncertainties are larger, in particular for the fainter secondaries when only a single-epoch spectrum is considered, and lower if surface gravities and the effective temperature ratio from previous detailed light curve and orbital dynamics studies are used as additional fit constraints. Uncertainties of elemental abundances are typically <0.10 dex. Some first applications of SATURN for analyses of new targets are shown to demonstrate its capabilities, such as fast rotators, including HD 149757 (ζ Oph). Consistent results are also found at reduced spectral resolutions relevant for observations with WEAVE and 4MOST.

MUSE-DARK: II. 3D morpho-kinematic modelling of lensed galaxies: Tully-Fisher relation of z ∼ 1 star-forming galaxies

First Author: Jeanneau, Alexandre
Instruments: MUSE
ProgramIDs: 094.A-0115, 095.A-0181, 096.A-0496, 096.A-0710, 0100.A-0763, 094.A-0525, 60.A-9345, 095.A-0653
BibCode: 2026A&A...709A.120J

Extending local kinematic studies to earlier cosmic times is valuable to understand how galaxies evolve in relation to their dark matter haloes. In a series of papers on lensed kinematics, we seek to combine the sensitivity of 3D forward modelling to low signal-to-noise ratio outskirts with the enhanced spatial resolution provided by cluster lensing. In this first paper, we (i) present and validate our methodology, which directly constrains the source parameters by incorporating lensing deflections into the GalPaK^3D forward-modelling algorithm, and (ii) investigate the evolution of the stellar-mass and baryonic-mass Tully─Fisher relations (sTFR and bTFR) since z ∼ 1 as a demonstration. We define a robust sample of strongly lensed star-forming galaxies (SFGs) from the MUSE Lensing Cluster survey, spanning magnifications μ = 1.4 − 12.4 and stellar masses M_★ = 10^8.1 − 10^10.3 M_⊙. Using a series of mock galaxies representative of our sample, we find that our method is significantly more reliable at recovering morpho-kinematic properties than approaches that ignore differential magnification, even for relatively modest magnifications (μ < 6). Restricting the analysis to 95 rotationally supported SFGs with well-constrained velocities, we find a significant evolution of the sTFR zero point ( ∆ b^sTFR = −0.42^+0.05_−0.05 dex ∆ b sTFR = − 0 . 42 − 0.05 + 0.05 dex in stellar mass) but no detectable evolution of the bTFR zero point ( ∆ b^bTFR = 0.00^+0.06_−0.06 dex ∆ b bTFR = 0 . 00 − 0.06 + 0.06 dex in baryonic mass) relative to z ≍ 0. Our results are consistent with a mild evolution of the stellar-to-halo mass ratio and support the view that the sTFR has evolved only weakly over the past ∼8 Gyr, aside from shifts driven by the redshift dependence of halo-defining quantities such as the critical density and overdensity. The absence of detectable evolution in the bTFR zero point suggests that the increasing contribution of cold gas mass at higher redshift fully compensates for the evolution observed in the stellar component alone.

The Longest-period Young Transiting Exoplanets—A Duo of Puffy Giants inside a Debris Disk

First Author: del Burgo, Carlos
Instruments: HARPS
ProgramIDs: 098.C-0739, 1101.C-0557, DataDoiProID
BibCode: 2026ApJ..1003L..15D

We identify two large-radius planets around the F-type star HD 114082 as the longest-period young transiting exoplanets known. From the first transit, detected by NASA's Transiting Exoplanet Survey Satellite (TESS), and a second dip, spotted by the Next-Generation Transit Survey (NGTS), we predicted midtransit times for HD 114082 b (planet b). We pinpoint its orbit (period P_b = 225.5504 ± 0.0004 days) from a third transit captured with the ESA's CHaracterising ExOplanet Satellite and the upgraded Antarctic Search for Transiting ExoPlanets telescope (ASTEP+), alongside orbit-discriminating observations. Another dimming partly covered by ASTEP+ completes the four-transit series. We support with dynamical evidence the planetary nature of a deeper transit detected with TESS and NGTS, identifying planet c. Additionally, we reexamine the debris disk, fitting its excess emission with two dust components. Fundamental stellar parameters are inferred from stellar evolution models, while a joint modeling of photometric and radial velocity time series yields the planetary parameters, with masses further constrained using an N-body code. For planet b, the semimajor axis a_b = 0.791 ± 0.008 au, eccentricity e_b ≍0, inclination i_b = 89 .° 791 ±0.014, radius R_b = 1.046 ± 0.014 R_J, and 95% confidence upper limit on its mass M_95%,b = 1.6 M_J. For planet c, a_c = 0.99 −0.04+0.03 au, e_c ≍0, i_c = 89 .° 701 ±0.011, R_c = 1.36±0.03 R_J, and M_95%,c = 2.0 M_J (0.24 M_J if adding transit-timing-variation constraints). They seem to be moderate-to-low-mass giants in nearly resonant, coplanar, circular orbits that formed in situ, or beyond the snow line, and migrated inward, shaping the disk. *This study uses CHaracterising ExOplanet Satellite data observed as part of the Guest Observers programmes CH_PR240025 (PI: C. del Burgo) and CH_PR250012 (PI: C. del Burgo) and the Guaranteed Time Observation programmes CH_PR100017 and CH_PR140079.

PENELLOPE: IX. Lithium, iron, and barium elemental abundances in eight nearby young clusters

First Author: Carini, R.
Instruments: ESPRESSO, UVES, XSHOOTER
ProgramIDs: 106.20Z8
BibCode: 2026A&A...709A.144C

We conducted a homogeneous chemical analysis of pre-main sequence stars with effective temperatures ranging from ∼3000 K to ∼5500 K in eight nearby star-forming regions (SFRs): Chamaeleon I, η Chamaeleonis, Lupus, Orion OB1a, Orion OB1b, σ Orionis, Taurus, and Corona-Australis. Our study aims to: (1) derive the lithium (Li) abundance (A(Li)) and highlight the impact of veiling correction on both the A(Li) and age determination; (2) perform an iron (Fe) and barium (Ba) abundance analysis in regions with scarce previous measurements; and (3) investigate the possible Ba enhancement. The analyzed data were obtained as part of the PENELLOPE Large Program using the ESPRESSO, UVES, and X-Shooter instruments. We measured the equivalent width (EW) of the Li line (EW_Li) at λ = 6707.8 Å, from which A(Li) was derived using the curves of growth method. The Fe and Ba abundances have been measured through spectral synthesis analysis. Using the EAGLES code, we derived an upper limit on the age of the eight SFRs. Our findings underscore the necessity of veiling corrections on EW_Li, which can shift A(Li) and age estimates by up to ∼0.7 dex and ∼20 Myr, respectively. When accounting for veiling, the A(Li) distributions peak in a range between 3.3 and 3.8 dex for most clusters and the upper age limit is approximately 5 Myr for all SFRs. We successfully measured the mean Fe and Ba abundances in Lupus, Taurus, Cha I, and η Cha, finding slightly subsolar Fe abundances and a clear Ba overabundance, with [Ba/H] values reaching up to 0.75 dex.

Einstein Probe Discovery of EP J171159.4─333253: An Eclipsing Neutron Star Low-mass X-Ray Binary with Clocked Bursts

First Author: Wang, Y. L.
Instruments: ULTRACAM_NTT
ProgramIDs: 115.28E7
BibCode: 2026ApJ..1003...22W

EP J171159.4−333253 is a new neutron star low-mass X-ray binary discovered in outburst by the Einstein Probe (EP) on 2025 June 23, exhibiting clocked type I X-ray bursts, eclipses, and dips. In this paper, we report on the results of the X-ray spectral and timing analyses for EP J171159.4−333253 using data collected by EP and NuSTAR during the first 21 days of the outburst. The X-ray burst recurrence time can be characterized over a subset of nine bursts spanning 1.6 days around the NuSTAR observation, and the result is t_rec = 8196 ± 177 s, with indications of a possible decreasing trend. From the X-ray eclipse events, the binary orbital period and the eclipse duration are estimated to be P_orb = 6.48301 ± 0.00003 hr and D⋆,X=1245.5−6.5+6.9 s, respectively. These enable an estimate of the mass and radius of the companion star and the binary inclination, which are M₂ ≍ 0.6─0.8 M_⊙, R₂ ≍ 0.7─0.8 R_⊙, and i ≍ 73°─75°, respectively. We also report on joint ULTRACAM and EP observations on 2025 July 21─22, detecting the source optical counterpart and covering an eclipse in both X-ray and optical bands. The optical eclipse is wavelength dependent and broader than in X-rays, indicating that part of the optical emission arises from an extended region in the accretion flow. Despite a moderate variation in the source flux, the properties of the persistent X-ray emission are typical of a hard spectral state. We further evaluated the ratio of the accretion energy to the thermonuclear energy to be 120─130, implying helium bursts with the accreted hydrogen being depleted in between bursts.

Improved lanthanide constraints for the kilonova AT 2017gfo

First Author: Gillanders, J. H.
Instruments: XSHOOTER
ProgramIDs: 099.D-0382
BibCode: 2026MNRAS.548ag748G

Spectroscopic observations of the kilonova AT 2017gfo provide a unique opportunity to identify signatures from individual heavy elements freshly synthesized via the r-process, the nucleosynthetic channel responsible for producing

$\sim$

half of all trans-iron-group elements. Limitations in the available atomic data have historically hampered comprehensive line identification studies; however, renewed interest has led to the generation of improved (more complete and accurately calibrated) line lists for r-process species. Here we demonstrate the utility of such data, by exploiting newly generated line lists for the lanthanides to model the photospheric-phase 3.4 d X-shooter spectrum of AT 2017gfo with the radiative transfer tool TARDIS. We find the data can only be reproduced by invoking a substantially diminished lanthanide mass fraction (

$X_{{\small LN}}$

) than that proposed by previous studies. Specifically, our model necessitates

$X_{{\small LN}} \approx 2.5 \times 10^{-3}$

in the line-forming region, a value

$20 \times$

lower than previously claimed. This substantial reduction in

$X_{{\small LN}}$

is driven by our inclusion of much more complete lanthanide line information that enables better estimation of their total contribution to the observations. We encourage future modelling works to exploit all atomic data advances, and also encourage continued efforts to generate the necessary data for the remaining r-process species of interest.

Spectropolarimetry of the changing-look active galactic nucleus NGC 1566 and its potential link to supermassive black hole binaries

First Author: Marin, F.
Instruments: FORS2
ProgramIDs: 115.27X4
BibCode: 2026A&A...709A.188M

Context. The active galactic nucleus (AGN) NGC 1566 is known to present dramatic and regular spectral shape changes, associated with the appearance and disappearance of broad emission lines. Aims. The underlying mechanism responsible for such changes is yet to be identified, but occultation, eccentric accretion disks, turbulent disk-dominated broad line regions (BLRs) or binary supermassive black holes have been hypothesized. Methods. Because the scenarios used to explain the variable spectral shapes of NGC 1566 each have a specific geometric configuration, we used the Very Large Telescope (VLT) FOcal Reducer/low dispersion Spectrograph 2 (FORS2) instrument to obtain nine 3500─10 000 Å polarized spectra of the source between August 2 and September 21, 2025. Results. We caught the AGN in a type-2 state, i.e., without any broad component in total nor polarized fluxes. Its low (0.22─0.24%) and wavelength-independent polarization degree (and angle) above 4000 Å argues against occultation of the BLR and is consistent with a significant weakening or disappearance of the BLR. The polarized spectrum reveals a strong rise of polarization in the blue band, likely echoing the 2018 outburst of the AGN. The temporal variability of the total flux continuum but the steadiness of the line profiles demonstrate that the object is viewed close to pole-on, irrespective of its spectral type at the time of observation. Relative to archival data, NGC 1566 shows significant variability in polarization degree, angle, and wavelength dependence, transitioning from gray to chromatic polarization. Even more surprisingly, NGC 1566 behaves opposite to the basic predictions of the unified model: its polarization angle is perpendicular to the AGN polar axis and its polarization degree is higher when in a brighter, type-1 phase. Conclusions. The results reported above contradict occultation and binary supermassive black hole hypotheses. They support, rather, accretion-driven photoionization and/or structural changes in the internal accretion flow and the BLR, but their geometry can only be probed by new spectropolarimetric campaigns during a type-1 phase of NGC 1566.

Recovering extratidal open cluster members via multi-elemental chemical tagging

First Author: Piatti, Andrés E.
Instruments: FLAMES, GIRAFFE, UVES
ProgramIDs: 188.B-3002, 193.B-0936
BibCode: 2026MNRAS.548ag804P

The identification of open cluster (OC) members has been revolutionized by high-precision Gaia astrometry, yet traditional kinematic membership selections remain inherently conservative, often overlooking stars in tidal tails or those with perturbed velocities. This study investigates the reliability of these kinematic probabilities by searching for leaky cluster members ─ stars that fail standard kinematic membership criteria (

$P \lt 0.7$

) but possess chemical signatures identical to their host clusters. Using high-resolution spectroscopic data from the Gaia-European Southern Observatory Survey, we established a seven-element chemical fingerprint ([Fe/H], Li, Si, Ca, Ti, Co, and Ni) for 34 OCs. We identified a sample of 63 stars across 22 clusters that are chemically indistinguishable from their host populations despite being kinematically rejected by standard algorithms. By cross-referencing these targets with Jacobi radii (

$r_\mathrm{ J}$

) derived from modern Milky Way potential models, we find that 35 per cent are located in extratidal regions (

$d \gt r_\mathrm{ J}$

), providing direct evidence of active cluster dissolution and tidal debris. The remaining 65 per cent are located within the Jacobi radius, suggesting that their kinematic rejection is likely due to orbital motion in unresolved binary systems. These results demonstrate that chemical tagging is a critical tool for overcoming the spatial and kinematic biases of astrometric catalogues. By recovering these lost members, we provide a more complete census of cluster mass-loss and underscore the necessity of a hybrid chemical-kinematic approach to map the transition of stars from bound systems to the Galactic field.

Modelling the non-equilibrium chemistry of the Milky Way's cold nuclear wind

First Author: Noon, Karlie A.
Instruments: PI230
ProgramIDs: 0104.B-0106
BibCode: 2026MNRAS.548ag715N

Cold atomic and molecular gases are commonly observed in the winds of both external galaxies and the Milky Way, yet the survival and origin of these cool phases within hot galactic winds is poorly understood. To help gain insight into these problems, we carry out time-dependent chemical modelling of cool clouds in the Milky Way's nuclear wind, which possess unusual molecular-to-atomic hydrogen ratios that are inconsistent with both disc values and predictions from chemical equilibrium models. We confirm that CO and

${\rm H} \,{\small I}$

emission comparable to that in the observed nuclear wind clouds cannot be produced by gas in chemical equilibrium, but that such conditions can be produced in a molecule-dominated cloud that has had its atomic envelope rapidly removed and has not yet reached a new chemical equilibrium. Clouds in this state harbour large reservoirs of molecular gas and consequently have anomalously large CO-to-H

$_2$

conversion factors, suggesting that the masses of the observed clouds may be significantly larger than suggested by earlier analyses assuming disc-like conversions. These findings provide a new framework for interpreting cold gas in galactic winds, providing strong evidence that cold outflows can originate from the galactic disc molecular clouds that survive acceleration into the wind but lose their diffuse atomic envelopes in the process, and suggesting that the Milky Way's nuclear outflow may be more heavily mass-loaded than previously thought.

Mapping the Extended Lyα Emission within the Circumgalactic Medium of Quasars Hosted by Dusty Starbursts with CubeCarve

First Author: Hall, Kevin
Instruments: MUSE
ProgramIDs: 0102.A-0403, 0103.A-0296, 0102.A-0428
BibCode: 2026ApJ..1002..216H

We present a study of extended Lyα emission around four quasars hosted by dusty starbursts, which are composite systems thought to represent a transitional stage in quasar evolution. To extract faint circumgalactic medium (CGM) emission in the presence of bright point sources, we introduce CubeCarve, a dual-channel deconvolution algorithm that separates unresolved quasar emission from spatially extended structure. This approach enables reliable recovery of Lyα emission projected onto the quasar position without introducing subtraction artifacts. Using CubeCarve v1.0.0, we find that the Lyα surface brightness profiles of these systems are, on average, fainter and shallower than those of quasars of similar bolometric luminosities. We also find that the total integrated Lyα luminosities of the nebulae are lower in systems whose host galaxies exhibit brighter far-IR emission. These results suggest that the CGM conditions in composite systems differ from those in the broader quasar population. Our study highlights both the physical diversity of quasar CGM environments and the effectiveness of CubeCarve for recovering diffuse emission in modern integral-field unit datasets.

TOI-4552 b: A new ultra-short-period rocky world revealed by NIRPS and TESS

First Author: Srivastava, Avidaan
Instruments: HARPS, NIRPS
ProgramIDs: 111.254T
BibCode: 2026A&A...709A..73S

Context. A particularly intriguing subclass of rocky exoplanets are ultra-short-period worlds, which orbit their host stars in less than a day. These planets are particularly rare around M dwarf stars, and only ten of them have a constrained mass and radius so far. Aims. We present the validation and characterisation of the ultra-short-period (0.3 days) Earth-sized planet TOI-4552 b orbiting a nearby (27.26 pc away) M4.5V dwarf. Methods. We complemented TESS photometry ground-based transit observations from LCO, ExTrA, and SPECULOOS to validate the planetary radius, and we cleared the field of any contaminants. Speckle imaging with Zorro (Gemini-S) rules out false-positive scenarios caused by eclipsing binary sources. Spectroscopic observations with NIRPS and HARPS were used to obtain stellar abundances, constrain the planetary mass, and estimate the orbital parameters in conjunction with the transit observations. Results. TOI-4552 is a quiet star. It lacks short-term stellar variations in photometric or radial velocity data that might be associated with stellar rotation. Long-term photometric data from ASAS-SN also suggest a lack of activity signals. TOI-4552 b (M_p = 1.83 ± 0.47 M_⊕, R_p = 1.11 ± 0.04 R_⊕) lies between the Earth-like and iron-rich composition tracks on the mass-radius diagram. The exopie interior structure model, without constraints from refractory abundance ratio, yields a core mass fraction of 0.54_−0.25^+0.17 and a bulk density of 7.74±2.14g/cm³. Since the core mass fraction spans a wide range because the uncertainty on the mass is high, the definitive interior composition cannot be determined with the current dataset. Conclusions. TOI-4552 b probably is marginally richer in iron than the Earth, but confirmation of its status requires additional precise radial velocity measurements. Combined with its high emission spectroscopic metric (ESM = 19.5), negligible stellar activity, and short orbital period, TOI-4552 b emerges as a compelling target for atmospheric and surface composition studies with JWST.

Characterization of Type Ibn Supernovae

First Author: Farias, D.
Instruments: EFOSC2
ProgramIDs: 199.D-0143, 1103.D-0328
BibCode: 2026A&A...708A.270F

Context. Type Ibn supernovae (SNe) are characterized by narrow helium (He I) lines from photons produced by the unshocked circumstellar material (CSM). About 80 SNe Ibn have been discovered to date and only a handful of them have extensive observational records. Thus, many open questions remain regarding the progenitor system and the origin of CSM. Aims. Here, we investigate potential correlations between the spectral features of the prominent He I λ5876 Å line and the optical and X-ray light curve properties of Type Ibn SNe (SNe Ibn). Methods. We compiled the largest sample of 61 SNe Ibn to date, of which 24 SNe have photometric and spectroscopic data available from the Young Supernova Experiment and 37 SNe benefit from archival datasets. We fit 24 SNe Ibn with sufficient photometric coverage (B to z bands) using semi-analytical models from MOSFiT. Results. We demonstrate that the light curves of SNe Ibn are more diverse than previous analyses suggest, with absolute r-band peak magnitudes (r_max) of −19.4 ± 0.6 mag, along with rise (from −10 days to peak, γ₋₁₀) and decay rates (from peak to +10 days; γ₊₁₀) of −0.08 ± 0.06 and 0.08 ± 0.03 mag/day, respectively. We find that the majority of SNe Ibn in the subsample are consistent with a low-energy explosion (< 10⁵¹ erg) of a star with a compact envelope surrounded by ~0.1 M_⊙ of helium-rich CSM. The inferred ejecta masses are small (M_ej ~ 1 M_⊙) and expand with a velocity of ~5000 km/s. Our spectroscopic analysis shows that the mean velocity of the narrow component of the He I lines, associated with the CSM, peaks at ~1100 km/s. Conclusions. The mean CSM and ejecta masses inferred for a subsample of SNe Ibn indicate that their progenitors are not massive (~10 M_⊙) single stars at the moment of explosion; rather, they are likely to be binary systems. This finding is in agreement with detections of potential companion stars of SNe Ibn progenitors and inferred CSM properties from stellar evolution models.

SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program: I. Analysis of the close surroundings of direct imaging companions

First Author: Lazzoni, C.
Instruments: SPHERE
ProgramIDs: 113.26GK, 114.276W, 111.24UH, 112.25QU
BibCode: 2026A&A...712A.189L

Aims. We searched for satellites and circumplanetary or circumsubstellar disks around directly imaged substellar companions, exploring their immediate environment to constrain the conditions for satellites and disk formation. Methods. We conducted a dedicated survey of 12 planets and brown dwarfs with VLT/SPHERE using a novel application of the starhopping technique. By building libraries of contemporaneous point spread function (PSF) references from nearby stars, we applied a frame-by-frame subtraction of each companion's flux using the negative fake companion method. This approach mitigates temporal PSF variability and enhances sensitivity to faint circumplanetary features. We derived contrast curves, translated them into mass detection limits using evolutionary models, and constrained the dynamically stable regions through estimates of Hill radii from orbital fits. Results. Our analysis yielded stringent limits on the presence of massive satellites, generally excluding companions more massive than a few Jupiter masses at separations beyond ~1--5 au, depending on each system's Hill radius. In most cases, no convincing point-like or extended residuals were found. However, we identified promising signals for three systems: extended residuals consistent with a circumplanetary disk around CT Cha b, tentative repeated residuals near TYC 8047-232-1 B that may trace a bound satellite companion of 3--6 M_Jup, and marginal residual signals at the location of the previously reported candidate around DH Tau b, whose interpretation, however, remains uncertain due to possible contamination by instrumental effects. These results confirm the power of star hopping in reducing PSF-related artifacts and provide some of the most stringent constraints to date on the mass and location of potential satellites and disks around directly imaged substellar companions.

Characterization of seven longer period eclipsing binary systems

First Author: Wells, Tony
Instruments: HARPS
ProgramIDs: 1101.C-0721, 106.212H
BibCode: 2026MNRAS.551g1401W

We report a joint analysis of TESS photometry and MINERVA-Australis spectroscopic observations for seven long-period eclipsing binary systems with F- and early-G-type dwarf primaries: TIC 37606218, TIC 73723286, TIC 172462064, TIC 220567625, TIC 270805930, TIC 308050066, and TIC 308991822. The companions are late-K to late-M dwarfs with orbital periods of

$\sim$

7--24 d, with all but one system exhibiting significant eccentricity. The combination of low-mass companions and relatively long orbital periods place these binaries in a regime where tidal interactions are comparatively weak, making them valuable benchmarks for testing low-mass stellar models with minimal tidal contamination. For the systems analysed here, together with those from our previous studies, we find that the radii and effective temperatures of the low-mass companions are broadly consistent with MIST isochrone predictions, with only a modest mean radius anomaly of

$\sim 1~{{\ \rm per\ cent}}$

and no statistically significant temperature anomaly. We furthermore find no compelling evidence for correlations between either anomaly and orbital period or metallicity, suggesting that the processes commonly invoked to explain the radius--temperature anomaly are either not the dominant drivers, or operate much less efficiently in the longer-period regime.

Revealing α-element's Past with Subaru/IRD: Oxygen Abundance of 35 Very Metal-poor Stars from Near-IR OH Lines

First Author: Setyo Budi, Bakuh Danang
Instruments: ESPRESSO, HARPS, UVES
ProgramIDs: 0104.D-0059, 090.B-0605, 165.N-0276, 71.B-0529, 68.D-0546, 273.D-5032, 111.251N, 073.D-0590, 0103.D-0118, 080.D-0347
BibCode: 2026ApJ..1008...75S

Oxygen abundances in very and extremely metal-poor (V/EMP) stars provide critical constraints on early massive stars' nucleosynthesis. An oxygen abundance analysis is presented for 35 V/EMP stars (-4.0 < [Fe/H] < -1.5) using near-infrared (NIR) H-band OH vibrorotational lines from high-resolution Subaru Infrared Doppler spectra. To examine the reliability of these NIR OH lines, the results are compared with the abundances obtained from the 3D non--local thermodynamic equilibrium (NLTE)-insensitive forbidden [O I] 6300 Å line using archival high-resolution optical spectra. After homogeneously rederiving stellar parameters and 1D/NLTE Fe abundances using Gaia photo-astrometry and literature optical Fe equivalent width data, oxygen abundance from OH and [O I] lines is determined through 1D local thermodynamic equilibrium (LTE) spectral synthesis. A sensitivity analysis confirms that NIR OH lines are highly sensitive to the adopted temperature ( ∆logϵ(O)/∆T~±0.25dex/±100K ) compared to the forbidden line. A temperature-dependent discrepancy between the tracers is identified: in cool red giants (T_eff ≲ 4600 K), OH-based abundances are systematically lower than [O I]-based abundances by 0.05--0.25 dex, while warmer red giants show higher OH-based abundances as expected from 3D effects. Despite this systematic offset, the numerous measurable NIR OH lines yield significantly smaller random abundance errors than that of the single, weak [O I] line. Leveraging this statistical precision, an empirical calibration as a function of T_eff, logg , [Fe/H], and [C/Fe] is derived to align the 1D/LTE OH abundances onto the [O I] scale. Applying this correction substantially reduces the scatter and temperature dependence in the [O/Fe] versus [Fe/H] plane and flattens the trend, bringing the results into fairly good agreement with Galactic chemical evolution models.

The Neptunian ridge planet WASP-156 b does not have a polar orbit

First Author: Lafarga, M.
Instruments: ESPRESSO, HARPS
ProgramIDs: 109.23FU, 0102.C-0618
BibCode: 2026MNRAS.551ag996L

The population of short-period exo-Neptunes is thought to be shaped by an interplay between different dynamical mechanisms, such as orbital migration and tidal effects, and photoevaporation. We can gain insight into these processes by studying observables such as the stellar obliquity. Here, we study the Rossiter--McLaughlin (RM) effect and measure the projected obliquity,

$\lambda$

, of the Neptunian ridge planet WASP-156 b. We analyse new ESPRESSO and MAROON-X spectroscopic transit observations, and new Next-Generation Transit Survey (NGTS) photometry simultaneous to the ESPRESSO data. Our analyses show an aligned orbit (

$\lambda =-8\pm 16^{\circ }$

, based on the ESPRESSO observations), in contrast to a previous report of a highly misaligned orbit. We also find the star's projected rotational velocity to be

$v \sin i_\mathrm{\star } \le 2$

$\mathrm{km\, s^{-1}}$

from spectral line modelling and

$v \sin i_\mathrm{\star } =0.40\pm 0.11$

$\mathrm{km\, s^{-1}}$

from the RM modelling. This is lower than the previously reported value of

$\sim 4$

$\mathrm{km\, s^{-1}}$

, which could partly explain the previously derived polar orbit. We also update the system's orbital parameters and rule out Jupiter-mass companions within 5 au using long-term radial velocity data. The planet's aligned and circular orbit (

$e\lt 0.16$

$3\sigma$

), and lack of nearby massive companions, are consistent with in situ formation or early disc-driven migration. Our findings move WASP-156 b from a tentative cluster of close-in Neptunes in polar orbits to the group of aligned Neptunes.

Detailed abundance determination of metal-poor stars with X-Shooter - II. Chemically disentangling the halo, disc, and GSE

First Author: Lowe, Benjamin D. C.
Instruments: XSHOOTER
ProgramIDs: 113.26N5, 115.28C7
BibCode: 2026MNRAS.551g1504L

We present a detailed chemical analysis of seven extremely metal-poor (EMP) star candidates observed with X-Shooter, combining them with 16 EMP candidates from Paper I. We measured abundances for 16 elements, showing excellent agreement with previously published results. The sample was further extended using high-resolution literature data for 315 metal-poor stars. The full sample was then kinematically separated into prograde disc, retrograde disc, GSE (Gaia-Sausage Enceladus), and halo classifications. Combining dynamics with chemistry, we demonstrate that the prograde disc exhibits a distinct negative linear trend in

$\left[\rm {Sc/Mg}\right]$

with increasing metallicity, with a slope of

$-0.6$

dex per dex. This contrasts with the halo trend at

$-0.04$

dex per dex, a difference significant at the

$3.95\sigma$

level. Within the metallicity range

$-4.2 \le [\mathrm{Fe}/\mathrm{H}] \le -1.9$

, the prograde disc trend is driven by low

$\left[\rm {Mg/Fe}\right]$

at lower metallicities, along with low

$\left[\rm {Sc/Fe}\right]$

at higher metallicities. This could be due to reduced early Mg enrichment in the progenitor prograde disc, followed by subsequent Mg enrichment, possibly associated with a later gas accretion event. However, the physical origin of the higher-metallicity Sc depletion remains unexplained by current nucleosynthesis models. The result remains significant at the

${\gt} 3\sigma$

level across kinematic classifications derived from a different Galactic potential. Additionally, we also identified an r-I star with enhanced Ti, moderately enhanced Sc, and depleted in C (unrelated to its evolutionary state). These abundances suggest a massive jet-induced hypernova progenitor, though a measurement of Zn is needed to verify this.

Unmasking (44) Nysa: Evidence for a trilobate structure

First Author: Minker, K.
Instruments: SPHERE
ProgramIDs: 116.2AQK
BibCode: 2026A&A...712L..26M

Context. (44) Nysa is one of the largest known E-type asteroids. Light curve inversion models have indicated that it may have an elongated shape commonly found in large binary systems. Aims. We aimed to identify the morphology and presence of possible satellites orbiting Nysa. Methods. We observed Nysa with the visible-wavelengths adaptive-optics instruments SHARK-VIS and SPHERE/ZIMPOL in order to image the object with the highest possible spatial resolution and visually identified surface features on the object. A shape model was constructed from these images and photometric light curves using the ADAM code. Results. Imaging revealed a highly unusual morphology with multiple distinct surface features, including two distinct valleys that are most easily interpreted as colli. A faint satellite was identified in the deconvolution residuals in multiple datasets. Conclusions. We determine that (44) Nysa is a binary system most likely consisting of a contact-trinary or highly-irregular, coherent primary object and a small satellite.

Pinning Down the Geometry of the Type Ic Broad-line Supernova 2026gzf

First Author: Wen, Xudong
Instruments: FORS2
ProgramIDs: 116.2ASW, 116.28T2
BibCode: 2026ApJ..1008L...3W

Type Ic broad-line supernovae (SNe Ic-BL) are often associated with energetic explosions that display a prompt outburst of high-energy emission. Since their progenitor lost the H and He envelopes before the explosion exposing the C/O core, their explosion dynamics and geometry can be seen in an unobscured and undistorted way. We present imaging polarimetry and spectropolarimetry of the Type Ic-BL SN 2026gzf obtained 4.6 and 16.5 days after the X-ray shock breakout, which was recorded by the Einstein Probe satellite as EP260321a, showing it to be one of the softest and intrinsically dimmest extragalactic fast X-ray transients. The persistent low continuum polarization indicates that the outer layer of SN 2026gzf is mostly spherical, suggesting the explosion did not significantly disrupt the progenitor envelope. At day 16.5, the calcium near-infrared triplet displays a peak polarization above 1.5%. The geometry of the associated line opacity is also compatible with an axisymmetric configuration. The spatial distribution of such oxygen-burning ashes thus indicates the presence of a symmetry axis of the excitation structure within the nearly spherical ejecta. The Ca,II triplet polarization is dominated by a primary component spanning ∼25,000─40,000 km s⁻¹, while a possible high-velocity polarization substructure of modest statistical significance may indicate a complex, nonaxisymmetric excitation geometry in the outer ejecta. By implementing a three-dimensional Monte Carlo calculation, we infer that a viewing angle of ∼40^∘ from the symmetry axis of the excitation structure could plausibly reproduce the observed spectral and polarization profiles of the Ca II triplet.

X-Shooter survey of disc accretion in Upper Scorpius: II. A lack of correlation between accretion rates and disc properties

First Author: Empey, A.
Instruments: XSHOOTER
ProgramIDs: 111.255B, 115.27XL, 105.2082, 113.26NN, 0101.C-0866, 097.C-0378
BibCode: 2026A&A...712A.222E

Context. The evolution of protoplanetary discs is intertwined with the process of planet formation, growth and migration. Studies of nearby star-forming regions of different ages and properties provide the information needed to understand the processes governing their evolution. Aims. This paper presents the results of a spectroscopic study of the stellar and accretion properties of a large sample of 127 stars with protoplanetary discs in the Upper Scorpius region, a relatively old (5--10 Myr), nearby (~145 pc) star-forming region, with disc dust masses inferred from ALMA continuum measurements. Methods. We derived the accretion luminosity from the excess UV continuum emission with respect to the photospheric and chromospheric emission self-consistently with the stellar spectral types, extinction, and luminosity, using the FitteR for Accretion ProPErties of T Tauri stars (FRAPPE) code. We applied a new method to evaluate upper limits on the accretion luminosity. In ~50% of cases, we could only evaluate upper limits on the accretion luminosity, either because the signal-to-noise ratio of the data was insufficient or because the measured value of the accretion luminosity was below the statistical estimate of the emission due to chromospheric activity. Results. The mass accretion rate shows a weak correlation with stellar mass, while we find no correlation with disc properties such as dust mass or gaseous disc radius. The dispersion is larger than that found in younger star-forming regions such as Lupus and Chamaeleon I, and suggests fading of the correlations with age. We find no evidence that the observed dispersion can be explained by membership in Upper Scorpius sub-groups, or by the properties of known binary systems or transition discs. Conclusions. The lack of correlation and the large dispersion of accretion rates challenge the current expectations of evolutionary models. The observed properties point to a decoupling of the inner and outer discs by the age of Upper Scorpius and a fading of the relations observed in younger star-forming regions, which calls for further development of current theoretical frameworks to be explained. ★ Based on observations collected at the European Southern Observatory under ESO programmes 097.C-0378(A), 0101.C-0866(A), 113.26NN.001, 113.26NN.003, 115.27XL.001, and 105.2082.003.

SaNDi-SHoP: Searching for Satellites'N'Disks with a Star-Hopping Program: II. Spectrophotometric analysis and orbital monitoring of directly imaged companions

First Author: Bernardi, A.
Instruments: SPHERE
ProgramIDs: 095.C-0298, 198.C-0209, 1100.C-0481, 096.C-0241, 097.C-0865, 111.24UH, 112.25QU, 113.26GK, 114.276W
BibCode: 2026A&A...712A.190B

Context. Over the past decade, advances in high-contrast imaging instrumentation, coupled with extreme adaptive optics systems, have enabled the discovery of tens of planets and brown dwarfs orbiting at wide separations from their host stars (a ≳ 10 au). The existence of companions at these separations challenges current planet-formation paradigms, highlighting the importance of high-contrast imaging as the only technique capable of directly probing this region of planetary systems. Aims. In this paper, we present a survey of thirteen planets and brown dwarfs observed with VLT/SPHERE between June 2023 and July 2025. These data provide updated photometry in the 1.0--1.7 µm range and new high-precision astrometry, enabling tighter constraints on their orbital properties. Methods. We used the IRDIS subsystem to acquire dual-band H2H3 images (λ_H2 = 1.593 µm, λ_H3 = 1.667 µm) for all companions in our sample. For the three objects located within the IFS field of view (GQ Lup B, PZ Tel B, and HD 984 B), we additionally obtained low-resolution (R ~ 50) near-infrared (0.96--1.34 µm) spectra. We combined our new astrometric measurements with those available in the literature to derive updated orbital solutions. The orbital fitting was performed using the orbitize! Python package. For CT Cha b, HIP 78530 B, HIP 64892 B, and RX J1609.5--2105 b, this work provides the first orbital solutions to date. Results. We derived new photometry for all objects, which, when compared with field dwarfs in color--magnitude diagrams, indicates spectral types ranging from mid-M to mid-L. For the companions observed with IFS, their spectra are best matched by those of M6--M8.5 field dwarfs. Our updated orbital fits provide tighter constraints for nearly all companions and are consistent with non-circular orbits in all cases, potentially disfavoring core-accretion formation within their circumstellar disks.

A Face-on View of Interstellar Dust in the Galactic Plane

First Author: Zhang, Lin
Instruments: VIRCAM
ProgramIDs: 179.B-2002
BibCode: 2026AJ....172..177Z

Interstellar dust is a fundamental component of the Milky Way, influencing star formation, galactic evolution, and observations across the electromagnetic spectrum. Using red clump stars selected from near- and mid-infrared photometry, together with stellar catalogs from previous studies, we construct dust density maps of the Galactic plane (∣Z∣ < 25 pc) covering the full 360° in longitude and reaching distances up to 7 kpc. By applying a U-Net convolutional neural network to invert the line-of-sight extinction distribution, we obtain dust density maps at resolutions of 10, 50, and 100 pc, which reveal detailed structures including spiral arms, inter-arm spurs, and giant cavities. The dust distribution in the Galactic plane exhibits a morphology closely resembling that of the so-called Phantom galaxy M74. The derived exponential scale length of the Galactic dust disk is 2.90 kpc, slightly larger than that of the stellar thin disk. Our publicly available dust maps provide a new benchmark for extinction correction, studies of Galactic structure, and the investigation of the interplay between star formation and the interstellar medium.

JWST PRIMER: post-starburst galaxies dominate the low-mass quiescent galaxy population since z ~ 2

First Author: de Lisle, Thomas
Instruments: FORS2, VIMOS
ProgramIDs: 194.A-2003, 094.A-0410, 180.A-0776
BibCode: 2026MNRAS.551g1496D

We present the evolution of the stellar mass functions for photometrically-selected star-forming, passive and post-starburst galaxies, based on James Webb Space Telescope PRIMER observations of the Ultra-Deep Survey (UDS) field. We identify over 800 post-starburst galaxies within the redshift range

$0.5 \lt z \lt 3.0$

. We confirm the presence of a low-mass upturn in the quenched galaxy mass function at

$\log (M_{\ast }/\mathrm{M_\odot }) \lt 10$

out to

$z\sim 2$

, and show it is primarily driven by post-starburst galaxies. These findings imply that a rapid quenching pathway for low-mass galaxies is already active by

$z \sim 2$

, which may be linked to environmental processes. If we assume that all post-starburst galaxies evolve into passive galaxies, adopting a typical visibility time for the post-starburst phase, we find a significant overprediction of low-mass passive galaxies at later times. We suggest a variety of factors that could contribute to reconciling this tension. If low-mass (

$M_{\ast } \lesssim 10^{10}\, \mathrm{{\rm M}_{\odot }}$

) post-starburst galaxies quench through slower channels than high-mass systems then the post-starburst phase may be visible for longer periods, reducing their contribution to the passive population. However, the maximum realistic visibility time-scale cannot account for all of the excess. We propose that additional factors inhibit the build-up of the low-mass passive galaxy mass function. These galaxies may be removed through mergers or tidal disruption, rejuvenate and return to the star-forming population, or represent systems observed during a dormant phase of stochastic star formation. We conclude that the emergence of the low-mass quenched population is likely governed by a complex interplay of processes, and cannot be explained by simple one-way evolutionary pathways.

The impact of interpolation in high-resolution spectroscopy: The overlooked role of interpolation in radial velocity extraction

First Author: Silva, A. M.
Instruments: ESPRESSO
ProgramIDs: 1102.C-0744, 1104.C-0350, 109.236P, 106.21M2, 108.2254, 0102.D-0346, 1102.C-0958
BibCode: 2026A&A...712A.159S

Aims. We explore the impact that spectral interpolation introduces in radial velocity (RV) time-series that are extracted using templatebased methods, in particular systematic biases induced in this process. Methods. We generate synthetic datasets with Gaussian profiles to evaluate the flux residuals and line asymmetry that are the result of changing the sampling location of the lines, induced by barycentric motion and instrumental drifts. We generate synthetic spectra as the sum of Gaussian functions whose parameters were determined through an observed spectrum. The s-BART pipeline was applied to such datasets, allowing us to evaluate any biases in RV extraction that are introduced by its internal and implicit assumptions in line shape. Lastly, we apply the s-BART pipeline to ESPRESSO observations of four stars, with different observation strategies: two that use high-cadence observations over a single night and two that have observations spread over multiple nights. When extracting RVs from stellar spectra, we change the interpolation algorithm used in the process of constructing the stellar template and, afterwards, during RV extraction. They are then compared with RVs extracted whilst using the widely used cubic-spline interpolation. Results. We find that the synthetic datasets reveal systematic biases with the largest peak-to-peak amplitudes reaching ~20 m s^-1 in low S/N cases, with the amplitude decreasing as the S/N of the spectra increases. In the extreme case of noise-free data, we still recover a systematic bias, albeit at the mm s^-1 level, significantly smaller than the RV precision of state-of-the-art instruments. When using real observations, we find that RV time series that use high-cadence observations with small BERV variation (barycentric motion comparable to the pixel size of the instrument) are impacted by the choice of the interpolation algorithm. This impact is smaller in cases of higher S/N, where the peak-to-peak amplitude reaches ~1 m s^-1. In the comparatively lower S/N case we find peak-to-peak residuals as large as ~25 m s^-1. In cases where the observations are spread over a larger BERV window, we find an upper limit of 20 cm s^-1 of RV scatter for this systematic signal. Conclusions. We conclude that diverse science cases are affected by the results presented in this manuscript, as the interpolation of stellar spectra is present in all of them to place observations in a common wavelength grid. This will impact not only the detection and characterization of exoplanets, but also atmosphere studies, asteroseismic analysis, and even cosmological red-shift determination.

A shot in the dark: searching for dark substructures in the RX J0437+00 galaxy cluster

First Author: Lagattuta, David J.
Instruments: MUSE
ProgramIDs: 106.21AD, 0104.A-0801
BibCode: 2026MNRAS.551g1146L

Obtaining a census of dark matter structures at low mass (

$\le 10^9 {\rm M}_\odot$

) can provide strong constraints on the nature of dark matter, though identifying such structures remains difficult. In this work, we study the galaxy cluster RX J0437.1+0043, taking advantage of its powerful `exotic' Hyperbolic-Umbilic (HU) lensing configuration to search for substructure candidates. Using a combination of high-resolution imaging, integral field unit spectroscopy, and gravitational lensing modelling, we report on a tentative detection of a dark matter subhalo (

$m_{\rm halo} = 2.27 \pm 0.83 \times 10^9 {\rm M}_\odot$

) near the vicinity of one of the largest HU images. We stress that this result is still preliminary and that deeper data and more advanced modelling techniques are needed to ultimately confirm this detection. Nevertheless, this work outlines the first steps towards understanding subhalo properties in dense cluster environments, developing HU cluster lenses as a potential new tool for investigating dark matter.

The CRIMSON survey I: super-stellar SiO in the directly imaged companion TWA 5 B from high-resolution M-band spectroscopy

First Author: Parker, Luke T.
Instruments: CRIRES
ProgramIDs: 114.27LL, 110.23RW
BibCode: 2026MNRAS.551g1050P

Silicon is a key refractory element in giant planet atmospheres, which governs the formation of magnesium-silicate clouds, and reflects the quantity of silicates accreted during formation. While observations of directly imaged giant exoplanets have focused on the measurement of volatile species (e.g. CO, H

$_2$

O), high-resolution spectroscopy with CRIRES+ M-band provides access to gas phase silicon chemistry in sub-stellar atmospheres, through the ro-vibrational band head of SiO at 4

$\mu$

m. Here, we present the first results of the CRIMSON survey of silicon chemistry in directly imaged companions with CRIRES+ M-band. We report the strong detection of gaseous SiO (S/N = 7.5) in the directly imaged companion TWA 5 B, with an atmospheric abundance of log(SiO) =

$-3.56^{+0.42}_{-0.32}$

VMR, providing access to the refractory content of the atmosphere. The high retrieved SiO abundance implies the absence of significant magnesium-silicate cloud condensation, and thus the atmospheric silicon abundance is contained almost entirely within the observed gas phase SiO. Using the detection of refractory silicon, together with strong detections of the volatile species CO (S/N = 9.1) and H

$_2$

O (S/N = 18.8), we measure a stellar C/O and a marginally sub-stellar O/Si and C/Si, but a super-stellar Si/H ([Si/H]

$_{\star }$

$1.41^{+0.42}_{-0.32}$

). Collectively, these volatile-to-refractory ratios are consistent with formation through core-accretion beyond the CO snowline, or gravitational instability followed by substantial solid enrichment. Finally, we discuss how gas phase SiO provides a unique diagnostic of the cloud properties in hot gas-giants, and can be used to probe the dominant cloud species forming across the directly imaged planet and isolated brown dwarf populations.

Toward 3D orbits of wide sdO/B binaries: I. Six composite systems spatially resolved with VLTI/GRAVITY

First Author: Deshmukh, K.
Instruments: GRAVITY
ProgramIDs: 116.28ZD
BibCode: 2026A&A...712L..19D

Hot subdwarf stars (sdO/Bs) are widely considered to be products of binary evolution. A significant fraction of them is found in long-period or wide binaries (P > 500 d) with main-sequence (MS) companions, likely resulting from a stable mass-transfer episode in which the MS companion stripped the hydrogen envelope of the sdO/B progenitor. Consequently, wide sdO/B binaries represent a key population in our pursuit of understanding stable mass transfer. They exhibit a modest range of orbital periods and eccentricities as revealed by long-term spectroscopic campaigns, although the component masses are only poorly constrained. We present the first long-baseline interferometry campaign to observe wide sdO/B + MS binaries and take the first step toward determining their 3D orbits and model-independent component masses. We targeted six composite sdO/B + MS systems with VLTI/GRAVITY and spatially resolved all of them. The projected physical separations range between 1 - 3 au, with uncertainties between 1 - 8%. When combined with complementary information from spectroscopic or astrometric observations, our precise measurements are crucial to constrain 3D orbits for these systems. We also identified a potential third component in BD +10° 2357, although additional data are necessary for a confirmation. In light of continued spectroscopic monitoring and the imminent Gaia Data Release 4, we strongly encourage expanding the interferometric sample presented here to establish new precise orbital and mass constraints for this key population of binary interaction products.

The outer rings of SN 1987A from year 1994 to 2024: Morphology, light curves, and optical to mid-infrared spectra

First Author: Rosu, S.
Instruments: MUSE
ProgramIDs: 110.25AR
BibCode: 2026A&A...712A.188R

Context. The outer rings (ORs) of Supernova SN 1987A were ejected some 20 000 years before the explosion. Their characterisation is crucial for constraining the properties of the progenitor of this famous SN. Aims. While numerous studies have investigated the SN ejecta, equatorial ring (ER), and reverse shocks in detail, very few were dedicated to the ORs. We aim to fill this gap and investigate the ORs' physical properties. We analysed data obtained over a long temporal period, from multiple instruments, and over a wide wavelength range from the optical to mid-infrared of the northern and southern ORs (NOR and SOR) of SN 1987A. We combined observations taken with the Hubble Space Telescope (HST) between 1994 and 2022, with VLT/MUSE in 2023, and with the James Webb Space Telescope (JWST) in 2022 and 2024. Methods. We measured emission flux in different regions of the ORs in narrow-band HST and broad- and narrow-band JWST/NIRCam filter images. We extracted optical and mid-infrared spectra for the ORs in the MUSE and JWST/MIRI/MRS data and measured emission-line fluxes. We analysed the evolution of the ORs clumps' morphology over time with HST. Results. The optical light curves of the ORs have shown a steady decline with time over the last 30 years, both in the Hα and [O III] λ 5007 filters. This behaviour is expected as the ORs were ionised by the initial SN UV flash and have been fading since then. The observations do not show any sign of interaction of the SN ejecta with the ORs, which would appear as a brightening in the ORs' optical light curve. We estimated the decay times for [O III] to be 900 and 630--730 days for the NOR and SOR, respectively, and for Hα+[N II] to be 15 870 and 7160 days for the NOR and SOR, respectively. We provide the first mid-resolution spectra of the ORs in the optical and mid-infrared. We constrained the temperature from the optical [N II] lines to 13 400--16 900 K and 11 800--14 500 K for the NOR and SOR, respectively. We constrained the electron density from the optical [S II] lines to 610--670 cm^-3 and 720--790 cm^-3 for the NOR and SOR, respectively. Conclusions. The spectra of the ORs differ significantly from the spectrum of the ER, not only in the detected lines, but also in the line ratios of given lines. The ORs will likely keep on fading in the coming years until the SN ejecta sweep up the ORs. Continued monitoring of SN 1987A and its ring system in the X-ray to mid-infrared is essential to capture this instant.

Angular clustering and bias of photometric quasars in the Kilo-Degree Survey Data Release 4

First Author: William, Anjitha John
Instruments: OMEGACAM
ProgramIDs: 177.A-3018, 177.A-3016, 177.A-3017
BibCode: 2026A&A...712A.196W

We investigate the angular clustering and effective bias of photometrically selected quasars in the Kilo-Degree Survey Data Release 4 (KiDS DR4). We update the previous photometric redshifts (photo-zs) of the KiDS quasars using Hybrid-z, a deep learning framework combining four-band KiDS images and nine-band KiDS+VIKING magnitudes. Hybrid-z is trained on the latest Dark Energy Spectroscopic Instrument (DESI) DR1 and Sloan Digital Sky Survey (SDSS) DR17 quasars matching with KiDS, and achieves average bias ⟨δz⟩< 0.01 and scatter ~0.04(1 + z) on a test sample. The updated catalog of ~157k quasars over 777 deg² is divided into four tomographic bins spanning 0.1 <= z_phot <= 2.7. In each bin, we measure the angular two-point correlation function and compare it with theoretical predictions for dark matter clustering. We estimate the best-fit scale-independent quasar bias, which increases from b ≈ 1.6 at z ≈ 0.6 to b ≈ 4.0 at z ≈ 2.2, and is well matched by a quadratic relation in redshift. Our clustering analysis indicates that KiDS quasars reside in dark matter halos of mass log₁₀(M_eff/h^-1 M_⊙) in the range ~12.7--12.9 and effective peak heights ν_eff rising from ~1.5 to 2.9 over our redshift span. We study two systematics that could affect the bias derivation: stellar contamination and the redshift distribution assumed in the theoretical modeling. The former has a negligible effect, whereas the latter significantly impacts the derived b(z), emphasizing the importance of redshift calibration. Our work is the first cosmological application of quasars selected from KiDS and paves the way for future extensions in the final KiDS DR5, the Legacy Survey of Space and Time, or the 4-metre Multi-Object Spectroscopic Telescope.

Fresh Accretion Event in the Spiral Galaxy ESO 119-055

First Author: Sil'chenko, Olga K.
Instruments: MUSE
ProgramIDs: 106.2155
BibCode: 2026AJ....172..149S

Through long-slit spectral observations of the early type disk galaxy ESO 119-055 and archival panoramic spectroscopy data, we studied the kinematics, excitation, and oxygen abundance of the ionized gas in the outer disk of the galaxy. We discovered the decoupled rotation of the gas and stars in the center so revealing the gas acquisition from outside after the stellar-disk formation. The inhomogeneous distribution of the gas metallicity over the disk gives the evidence in favor of a very recent accretion event, approximately 100 Myr ago. Among the H II regions that we detected in the disk of ESO 119-055, the probable source of the gas is identified—the remnant of a small metal-poor satellite accreted by the host galaxy.

HARPS abundances with Korg I: 22 element abundances for 426 red giant stars

First Author: Aquilina, Sarah E.
Instruments: HARPS, NIRPS
ProgramIDs: DataDoiProID
BibCode: 2026MNRAS.551g1404A

Large stellar surveys have revealed the global abundance structure of the Milky Way, but small high-fidelity spectral samples offer a critical complement of nucleosynthetic depth. We aim to access the encoded information in an ensemble of abundances by leveraging highest quality spectra. We used HARPS spectra (R = 115 000) to determine (

$T_{\rm eff}$

$\log (g)$

, [M/H],

$v_\mathrm{mic}$

, and

$v \sin i$

) and 22 element abundances (Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Fe, Ni, Zn, Sr, Y, Zr, Mo, Ba, La, Ce, Nd, and Eu) for 426 red giant stars at a median internal precision of

$\sim$

0.02 dex evaluated from analysing repeat observations of a subset of stars. Stellar parameters and line-by-line abundances were obtained using the modern spectral synthesis code KORG -- the first time it has been used for HARPS. Comparisons with the literature reveal good overall agreement. A minor 0.1 dex offset in metallicity and specific discrepancies in individual element abundances are attributed to local thermal equilibrium assumptions and inaccuracies in atomic data. We show that 22 individual elements can be collapsed into a generative 6-parameter latent-variable model of shared enrichment patterns expressed in different per-star fractions; this model accurately generates the abundances with a median

$\chi _{\mathrm{ reduced}}^2 = 6$

. We report element gradients with respect to selected elements from different nucleosynthetic families. These gradients are a measure of inter-element production efficiencies and indicate multiple r-process production sites. Our analysis shows that abundances occupy a low-dimensional subspace, but joint (gradient-based) information encodes nucleosynthetic signatures. We have developed a KORG-pipeline to apply across evolutionary states on high-resolution spectra to provide our precision catalogue to serve as empirical constraints on chemical evolution and as a set of benchmark red giant abundance measurements.

DESI Strong Lens Foundry. IV. Spectroscopic Confirmation of DESI Lens Candidates with VLT/MUSE

First Author: Lin, Emerald
Instruments: MUSE
ProgramIDs: 111.24UJ, 111.24P8, 113.267Q, 112.2614, 109.238W
BibCode: 2026ApJS..286....9L

We present integral field spectroscopic observations of 76 strong gravitational lens candidates identified with a residual neural network in the DESI Legacy Imaging Surveys, obtained with the Multi Unit Spectroscopic Explorer (MUSE) on ESO's Very Large Telescope. These observations are part of an ongoing effort to build a large, spectroscopically confirmed sample of strong-lensing systems for studies on dark matter, galaxy structure, and cosmology. Our MUSE program targets both lens and source redshifts, with particular emphasis on Southern Hemisphere systems. MUSE's wide spectral coverage and integral field capability allow for efficient identification of multiple sources, lens environments, and weak spectral features. Redshifts for lenses and sources were obtained via manual identification of spectral features in extracted 1D spectra. Our dataset includes systems with complex configurations, such as multiple source planes and group- or cluster-scale environments. We extracted and analyzed 223 spectra, successfully determining both the lens and the source redshifts for 55 gravitational lens systems. For an additional 15 targets, we measured the redshifts of the lenses but were unable to determine the redshifts of the background sources. Six targets were confirmed to not be gravitational lenses. The results presented here complement space-based imaging from our Hubble Space Telescope SNAP program and spectroscopic follow-up with DESI and Keck and have lasting legacy value for identifying interesting high-redshift sources and complex lensing configurations.

Stellar nucleosynthesis in the era of large surveys: S-process-polluted binaries in GALAH DR4

First Author: Escorza, A.
Instruments: UVES
ProgramIDs: 111.24UZ
BibCode: 2026A&A...712A.111E

Context. Binary interactions during the asymptotic giant branch phase can lead to the formation of chemically peculiar stars such as Ba-, CH-, and CEMP-s stars with overabundances of s-process elements as well as carbon. Only a few hundred of these stars have been subject to detailed chemical and/or dynamical studies, typically in non-homogeneous samples. Aims. We compile a systematic sample of s-process-polluted candidates using the fourth data release of the large spectroscopic survey GALAH. We also compare the chemical and orbital properties of these candidates with those of confirmed s-process-polluted stars to gain stronger evidence of their nature. Methods. GALAH DR4 uses neural networks and automatic spectral analysis methods as well as data of a lower spectral resolution than is normally used to characterise these objects. We therefore built a validation sample of s-rich stars before querying the survey, for which we obtained VLT/UVES and Mercator/HERMES high-resolution (>80 000) spectra and analysed them with traditional methods. We compared our stellar parameters and individual abundances with those of the survey and used this validation to define the thresholds that a star in GALAH DR4 must pass to be flagged as a good s-process-rich candidate. Based on our comparisons with the high-resolution complementary spectra, we defined thresholds on five quantities: [s/Fe] > 0.40 dex, [Y/Fe] > 0.22 dex, [Zr/Fe] > 0.26 dex, [Ba/Fe] > 0.19 dex, and [La/Fe] > 0.26 dex. Results. We identified 1059 stars in GALAH DR4 that are good candidates to be s-process-polluted stars, covering a broad parameter space (4000 K < T_eff < 6000 K, 0.5 dex < log g < 5.0 dex, −2.0 dex < [Fe/H] < 0.5 dex). They share many similarities with the samples of confirmed s-rich stars, especially their ratios of heavy over light s-elements, which strengthens our confidence in the purity of the sample. When we cross-matched the sample with the literature, we found that only 7% of the candidates have measured orbital periods and eccentricities. This limits a full comparison with confirmed Ba and related star samples for now. However, their binary fraction is, as expected, higher than the one we found for the full GALAH DR4 catalogue. Conclusions. Our sample of candidates is almost five times larger than the number of currently confirmed polluted stars. This and the fact that it has been homogeneously treated by the GALAH survey opens very interesting avenues to compare nucleosynthesis models as well as binary evolution models.

High-resolution Optical Methane Line List from Observations of Titan for Cross-correlation Studies

First Author: Rianço-Silva, Rafael
Instruments: ESPRESSO
ProgramIDs: 114.277N, 106.218L, 0103.C-0203
BibCode: 2026ApJS..286....1R

Exoplanet atmosphere characterization heavily relies on molecular spectroscopic data. Despite efforts to obtain comprehensive spectral libraries for the chemical characterization of exoplanet atmospheres, large gaps remain, particularly for larger molecules and higher frequencies at high spectral resolution. One key example is the methane (CH₄) optical spectrum. CH₄, the simplest hydrocarbon, is a crucial species for exoplanet atmosphere characterization and a possible biosignature. However, until now, high-resolution line lists at optical wavelengths for CH₄ have been very challenging to obtain either experimentally or computationally, leaving the high-resolution spectrum of CH₄ uncharacterized across most of the visible spectrum. This restricts exploration of CH₄ absorption in the optical regime, as upcoming instruments such as ELT-ANDES and VLT-RISTRETTO will start probing the atmospheres of ever-smaller exoplanets in optical wavelengths. To address this spectroscopic data limitation, we observed Titan's optical spectrum—dominated by CH₄ absorption—at the highest spectral resolution to date with VLT-ESPRESSO. From it, we produced an empirical, low-temperature high-resolution (R ∼ 190,000) line list of CH₄ in optical wavelengths, which we present here, with thousands of previously unidentified lines. We employ this CH₄ line list (RRS-2026) to build a template suitable for high-resolution cross-correlation spectroscopy (HRCCS) studies—a first for CH₄ in optical wavelengths. With this new line list, we performed the first HRCCS detection of CH₄ in the atmospheres of Titan and Jupiter using optical high-resolution spectra. This work sets the stage for the search for CH₄ in exoplanet atmospheres through HRCCS with current and future ground-based high-resolution optical spectrographs, showcasing how solar system observations provide useful products for exoplanet research.

Consistent multiwavelength spectral modelling of cool white dwarfs with carbon-polluted atmospheres

First Author: Farihi, Jay
Instruments: XSHOOTER
ProgramIDs: 098.D-0059, 097.D-0064
BibCode: 2026MNRAS.551g1393F

This work presents atmospheric modelling of multiwavelength spectra for eight cool white dwarfs with carbon-enriched atmospheres, with four each of spectral-type DQ and DQp. The Deslanders-d'Azambuja bands of C

$_2$

are detected in all six DQ stars that have data covering wavelengths shorter than 4000 Å. These bands are blue-shifted in the DQp types, consistent with that observed for the Swan bands, and reproduced with the same pressure distortion model. The coolest stars in the sample show significant near-infrared flux suppression, identified here as collision-induced absorption from dense helium, with trace hydrogen [H/He]

$\lt -6$

, estimated from the absence of CH features. Notably, the near-ultraviolet through near-infrared spectral energy distribution of WD 0038─226 is correctly reproduced using an atmospheric model with [H/He]

$=-6.8$

; however, beyond 2 μm the predicted flux is too high, and a carbon-free atmosphere is able to reproduce the mid-infrared observations well. The multiwavelength coverage permits accurate modelling characterization of these stars, including constraining the ionization equilibrium in fluid helium and the resulting density profiles. The densities found in this work are 2─3 times higher than determined in previous studies, approaching 2 g cm

$^{-3}$

for the coolest stars. Excluding the uncertain high masses obtained for the two coolest DQp stars, the sample stars have masses that are broadly consistent with those found for the wider white dwarf population, with no difference across the DQ-DQp temperature boundary.

The First Hours and Days of the 2021 Explosion of the Recurrent Symbiotic Nova RS Ophiuchii

First Author: Skopal, Augustin
Instruments: UVES
ProgramIDs: 105.20B6, DataDoiProID
BibCode: 2026ApJ..1007..142S

The accretion of matter onto a massive white dwarf (WD) can lead to repeated nuclear explosions on its surface over a timescale of years to decades. The seventh explosion of the recurrent symbiotic nova RS Ophiuchi (RS Oph) was recorded on 2021 August 8. In this paper, we examine its early evolution, from 9 hr before its optical maximum until day 42. We achieved our goal by modeling the spectral energy distribution (SED) using optical spectroscopy and simultaneous BVR_CI_C photometry, supplemented by JHKL photometry and ultraviolet spectroscopy from previous explosions in 2006 and 1985. Our SED models revealed an early stage of development of the ejecta bipolar structure, consisting of a flared, density-enhanced equatorial disk and low-density regions in bipolar directions. The comparability of the internal shocks' luminosity in the equatorial outflow, inferred from our model parameters, with the luminosity of the warm WD pseudophotosphere during its presence in the spectrum (until ∼day 42) confirmed that a significant part of its radiation originates from reprocessed shock emission. We explain the formation and evolution of the bipolar ejecta structure during RS Oph explosions by the rotation of the accreting WD. Such an ejecta structure provides a natural framework for the generation of strong internal shocks and, thus, γ-ray emission inside the ejecta.

MUSE-ALMA haloes XIII: kinematics and stellar properties of tidal features associated with gas-rich galaxies

First Author: Karki, Arjun
Instruments: MUSE
ProgramIDs: 096.A-0303, 0100.A-0753, 0101.A-0660, 0102.A-0370, 298.A-5017
BibCode: 2026MNRAS.551g1226K

Interactions between galaxies and their circumgalactic medium (CGM) can be observationally traced by extended tidal-like features. Interacting absorption-selected galaxies are galaxies that exhibit diffuse extended structures such as tidal features due to gravitational influence of other galaxies, and are associated with quasar absorbers. We report an analysis of 17 interacting galaxies associated with either H I or Mg II absorbers and their tidal features at 0.1

$\lesssim$

0.6 selected from a total sample of 3658 galaxies. These were detected in Hubble Space Telescope and Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) observations and spectroscopically confirmed to be associated with strong intervening quasar absorbers. We estimated stellar masses (

$M_{*}$

) of the tidal structures from spectral energy distribution fits and analysed the kinematics of these structures using emission lines detected in the MUSE data. Our main findings are as follows: (1) Interacting absorbing galaxies exhibiting tidal features have enhanced star formation rates (SFRs), specific star formation rates (sSFRs), SFR surface densities, dust reddening, while exhibiting comparable emission metallicities to absorbing galaxies without tidal interactions. (2) The tidal features have higher sSFRs but lower SFRs and lower dust reddening than their host galaxies. (3) There is no significant difference in Mg II

$\lambda$

2796 rest-frame equivalent width between interacting and non-interacting absorbing galaxies. However, absorbing galaxies with tidal features are more massive and are located at greater distances from quasar sightlines, possibly tracing more extended CGM. Together, these results highlight the CGM's influence traced by tidal features on the stellar and kinematic properties of the interacting absorbing galaxies.

Unraveling the Mystery of the Peculiar and Young Hot Jupiter CoRoT-2 b. II. Phase-resolved Emission Spectroscopy with Very Large Telescope/CRIRES+ and Gemini South/IGRINS

First Author: Kesseli, Aurora Y.
Instruments: CRIRES
ProgramIDs: 111.24WF
BibCode: 2026AJ....172..145K

Hot Jupiters are expected to be tidally locked and synchronously rotating due to their short orbital periods. These conditions create large day─night temperature contrasts and are thought to drive eastward superrotating jets. Indeed, the majority of hot Jupiters are observed to have the hottest region of the planet either at the substellar point or offset in the eastern direction. However, the full phase curve of CoRoT-2 b, observed with the Spitzer Space Telescope, exhibits robust evidence of a western hotspot offset. To determine the origin of this peculiar hotspot offset, we present phase-resolved high-resolution observations of CoRoT-2 b from the CRIRES+ spectrograph on the Very Large Telescope and the IGRINS spectrograph on Gemini South, covering both pre- and posteclipse phases (0.34─0.63). We detect the signal from the planet (signal-to-noise ratio > 4) in both pre- and posteclipse phases separately, and therefore perform separate cross-correlation and retrieval analyses at the two epochs. The phase-resolved retrievals show highly consistent abundances and C/Os, but prefer a hotter and more isothermal temperature─pressure profile at posteclipse phases, consistent with the phase-curve observations that indicated a western hotspot offset. By testing multiple hypotheses invoked to drive a western hotspot offset, we find the most likely explanation to be subsynchronous planetary rotation. We measure the planet's rotational broadening to be 2.24−0.77+0.81 km s⁻¹, whereas the expectation from tidally locked rotation is 4.37 ± 0.13 km s⁻¹ (2.6σ discrepant). Other observations, such as high-precision phase curves or eclipse mapping, would help to further confirm the western hotspot offset and subsynchronous rotation.

First planetesimals from DESI DR1: 12 highly metal-rich white dwarfs

First Author: Izquierdo, Paula
Instruments: XSHOOTER
ProgramIDs: 115.28GM
BibCode: 2026MNRAS.551g1353I

Metal-enriched white dwarfs provide a unique insight into the composition of exoplanet interiors. These stars accrete the debris of disrupted planetary bodies, and hence, measuring the stellar parameters and photospheric abundances yields the bulk compositions of the parent bodies. At present, over 1750 debris-accreting white dwarfs are known, but just a few dozen are sufficiently enriched to allow a detailed abundance study. Here, we report the analysis of 12 highly metal-enriched white dwarfs observed within the Data Release 1 of the Dark Energy Spectroscopic Instrument (DESI). We characterized their stellar parameters and photospheric metal abundances, and we identified between three and ten different elements in their optical spectra, including most of the rock-forming species: O, Mg, Si, Ca, and Fe. We conclude that the accreted bodies broadly resemble compositions found within the inner Solar system such as primitive meteorites, processed material, or planetary cores. Six of the systems allowed a more thorough analysis: four of the parent bodies are composed of dry rock-forming elements; and two of them of something akin to a water-rich planetesimal. Thus, this study establishes DESI as a potent survey for identifying metal-rich targets, yielding reliable compositions of accreted exoplanetary material.

JWST Unveils the Bimodal Nature of Lyα Emitters at 3 < z < 7: Pristine versus Merger-driven Populations

First Author: Ren, Jian
Instruments: MUSE, VIMOS
ProgramIDs: 094.A-0205, 095.A-0240, 096.A-0090, 097.A-0160, 098.A-0017, 094.A-0289, 095.A-0010, 096.A-0045, 1101.A-0127, 194.A-2003
BibCode: 2026ApJ..1002...72R

We present a systematic study of merging galaxies among Lyα emitters (LAEs) using James Webb Space Telescope/NIRCam high-resolution imaging data. From a large sample of 817 spectroscopically confirmed LAEs at 3 < z < 7 in the GOODS-S field, we identify late-stage mergers and interacting systems (late-stage mergers and galaxy pairs) with fractions of 39.4% ± 2.5% and 60.6% ± 6.3%, respectively. The late-stage merger fraction increases from ∼15% at z > 6 to 45%─50% at z = 3, while the interaction fraction rises from ∼45% at z > 6 to 70% at z < 4. These fractions exhibit significant redshift evolution and depend on both stellar mass (M_*) and UV magnitude (M_UV), being most prevalent in massive ( log(M⋆M⊙)>8.5 ) and bright (M_UV < −19.5) systems. At fixed M_* and M_UV, we find negligible differences in the UV slope (β) between late-stage mergers and isolated LAEs; however, a clear bimodal distribution emerges in the solar mass─specific star formation rate (M_*─sSFR) plane. Our results suggest the presence of two evolutionary classes: pristine LAEs, low-mass (M_* < 10^8.5M_⊙), isolated systems that likely represent early-stage galaxies with minimal merger activity; and merger-driven LAEs, massive (M_* > 10^8.5M_⊙) systems in which galaxy interactions may enhance star formation and/or facilitate the escape of Lyα photons, or involve mergers with less evolved LAE companions. These findings are consistent with existing observational and theoretical studies, and indicate that galaxy mergers can play an important, though not ubiquitous, role in shaping the evolution and observability of LAEs during the first 2 billion years of cosmic history.

JWST+ALMA Reveal the Buildup of Stellar Mass in the Cores of Dusty Star-forming Galaxies at Cosmic Noon

First Author: Bodansky, Sarah
Instruments: ALMA_Band_6
ProgramIDs: 2015.1.00543.S, 2017.1.00755.S
BibCode: 2026ApJ..1001..235B

Dusty star-forming galaxies (DSFGs) have long been suspected to serve as the missing evolutionary bridge between the star-forming and quiescent phases of massive galaxy evolution. With the combined power of JWST and the Atacama Large Millimeter/submillimeter Array (ALMA), it is now possible to use high-resolution imaging at rest-frame ultraviolet (UV), optical, near-infrared (NIR), and submillimeter wavelengths to study the multiwavelength morphologies tracing both the stellar populations and dust during this key phase. We present the joint analysis of JWST/NIRCam imaging in GOODS-S and millimeter dust emission traced by ALMA for a sample of 33 galaxies at z = 1.5─5.5 selected from the 1.1 mm GOODS-ALMA 2.0 survey, and compare the morphologies of this population to mass- and redshift-selected samples of field star-forming and quiescent galaxies. The 1.1 mm selected sample is morphologically distinct from other similarly massive star-forming galaxies; we find a steeper size-wavelength gradient from 1.5 to 4.4 μm, with a more dramatic decrease in size toward longer wavelengths. While the rest-NIR surface brightness profiles of the 1.1 mm selected galaxies are brighter in the inner regions relative to the field star-forming population, they are remarkably similar to the quiescent population. These morphological differences could suggest that DSFGs, unlike more typical star-forming galaxies, have already built up stellar mass in a severely dust-obscured core, leading to extended and clumpy morphologies at rest-UV and rest-optical wavelengths and more compact emission in the rest-NIR that is co-spatial with dust. If the bulge is already established, we speculate that millimeter-selected galaxies may imminently evolve to join their quiescent descendants.

The Solar Origin and Life Project: Detailed Characterization of Candidates for the Zero Age Main-sequence and Subgiant Stages

First Author: Eduardo-Oliveira, C.
Instruments: FEROS, HARPS, UVES
ProgramIDs: 076.C-0155, 076.C-0578, 083.D-0871, 086.D-0062, 087.D-0010, 087.D-0724, 089.D-0202, 090.C-0421, 096.C-0460, 097.D-0035, 0100.C-0097, 0100.D-0444, 183.C-0972, 192.C-0852, 198.C-0836, 072.C-0033, 072.C-0488
BibCode: 2026ApJ...999....6E

The context of the Sun in the Galactic neighborhood is not well understood, especially when we compare its physical properties to those of nearby stars. Thereby, we still cannot fully comprehend whether or not the Sun is a typical star. This work aims to identify and characterize stars aligned with the solar evolutionary track that could represent it at the zero age main-sequence and subgiant stages. We performed a spectroscopic analysis of 18 photometrically selected candidates using high-resolution and high-signal-to-noise ratio spectra as well as the classical spectroscopic method, based on the excitation and ionization equilibria of Fe I and Fe II lines. Additionally, we derived evolutionary parameters using isochrones, and kinematic parameters. We also estimated chromospheric activity levels and performed age estimates through three additional independent methods: activity─age relations using the Ca II H and K and Hα lines, and rotation periods estimated from TESS light curves. We identified three candidates that provide a good match to the Sun at ≍ 0.5 Gyr (HD 13531 and HD 61033) and subgiant (HD 148577) stages. Moreover, HD 197210 could be of interest when studying the Sun at ≍2 Gyr, when the Earth's atmosphere started having a significant amount of oxygen. Our selection method was successful, and we were able to identify stars similar to the Sun at different evolutionary stages, which is essential for future research in the search of exoplanets, and understand habitability, especially with the advent of the next generation of exoplanet-hunting instruments.

Observations of the Halo Star HD 177566

First Author: Dixon, William V.
Instruments: UVES
ProgramIDs: 092.C-0173, DataDoiProID
BibCode: 2026ApJ..1007..100D

We have analyzed archival far-ultraviolet (FUV) and optical spectra of the hot halo star HD 177566. The star has an effective temperature T_eff = 33,000 ± 1000 K, surface gravity logg=3.79±0.11 , and helium abundance logN(He)/N(H)=−0.86±0.05 . Abundances of 13 additional elements are consistent with those of other halo stars, save for carbon, which is underabundant by about 1 dex. The low-order hydrogen Balmer lines are not well reproduced by our models. The diffuse lines of He I are often broader than predicted, but the use of more recent line-broadening parameters significantly improves the fit. Scaling our best-fit model to the star's optical and near-IR magnitudes yields an extinction E(B − V) = 0.095 ± 0.005, consistent with the literature values, but the resulting model underpredicts the star's FUV flux by a factor of 2. The star's effective temperature and luminosity ( logL/L⊙=3.50±0.08 ) place it on the post-asymptotic giant branch (post-AGB) evolutionary tracks of a star that evolved from the red horizontal branch. Its low carbon abundance, logN(C)/N(O)=−2.18±0.21 , indicates that it did not experience significant third dredge-up while ascending the AGB.

A Cosmic Archipelago of lensed metal-poor galaxies at z ∼ 6

First Author: Bolamperti, A.
Instruments: MUSE, XSHOOTER
ProgramIDs: 094.A-0115, 111.253B, 0100.A-0763
BibCode: 2026A&A...712A.153B

The Cosmic Archipelago is an ensemble of galaxies, strongly lensed by the Hubble Frontier Fields cluster MACS J0416, displaying some of the most extreme physical properties known at z ~ 6.14. In this work, we combined JWST/NIRCam with deep VLT/X-shooter and JWST/NIRSpec IFU to perform a joint spectrophotometric analysis from the far-ultraviolet to the red-optical rest frame. In particular, we focused on CA4, a UV-faint (M_UV = −17.7), isolated, and compact (r_e = 81 ± 11 pc) galaxy at z = 6.1446, magnified by a factor of μ = 3.73. CA4 is a young, low-mass (M_* = 4.3 × 10⁶ M_⊙), star-forming (SFR = 0.46 M_⊙/yr), and metal-poor (Z ≃ 0.02 Z_⊙) galaxy that also serves as an efficient producer of ionizing photons (log(ξ_ion/erg⁻¹ Hz) ≃ 25.5). These properties place CA4 at the poorly explored interface between the regimes of massive stellar cluster and dwarf galaxies at the epoch of reionization (EoR). Moreover, CA4 presents large Lyα (f_esc^Lyα ∼ 43%) and Lyman-continuum (f_esc ∼ 47%) escape fraction values, consistent with the small Lyα velocity offset (∆v ∼ 100 kms⁻¹) and the extremely blue UV-continuum slope (β = −3.10). These characteristics suggest that such UV-faint, metal-poor galaxies may have a major contribution to cosmic reionization. Additionally, we confirmed five additional systems at the redshift of the Cosmic Archipelago, magnified by factors ranging from ∼1.2 to 12.5. They are all young (mass-weighted ages <11 Myr) and metal-poor galaxies (Z < 0.05 Z_⊙), spanning a wide range of stellar masses and star formation rates. Given the large number of these bursty star-forming galaxies in a relatively small cosmic volume, we estimated that all the currently known members of the Cosmic Archipelago result in a significant overabundance at z ∼ 6 (∆z ≃ 0.08), with a derived overdensity factor of δ_gal = 12.3_−4.6^+6.6. These results highlight the Cosmic Archipelago as an unprecedented laboratory for studying the earliest groups of low-mass and low-metallicity galaxies during the EoR.

The nucleosynthesis of Ba in the early Universe: Constraints from elemental abundances and isotopic ratios

First Author: Giribaldi, R. E.
Instruments: ESPRESSO, FLAMES, HARPS, UVES
ProgramIDs: 086.C-0284, 086.C-0448, 60.A-9700, 081.D-0531, 183.C-0972, 183.D-0729, 080.D-0347, 078.C-0233, 073.D-0590, 086.C-0145, 072.C-0488, 096.C-0053, 081.C-0802, 082.C-0427, 072.C-0513, 075.D-0760, 266.D-5655, 188.B-3002, 67.D-0554, 086.D-0871, 090.B-0605, 076.A-0463, 70.D-0474, 072.B-0585, 0104.D-0059, 60.A-9036, 192.C-0852, 196.C-0042, 295.C-5031, 0103.D-0310, 289.D-5015, 68.D-0546, 165.N-0276, 68.B-0618, 082.B-0610, 085.C-0063, 190.C-0027, 0103.D-0118, 0103.D-0616, 075.D-0600, 114.27JT, 079.D-0567, 076.B-0055, 083.B-0281, 65.N-0534, 167.D-0173, 67.D-0086, 077.B-0507, 71.B-0529, 077.D-0299, 68.D-0094, 65.L-0507, 076.B-0133, 68.B-0475, 074.B-0639, 093.D-0095, 67.D-0439, 095.D-0504, 078.B-0238, 080.D-0333
BibCode: 2026A&A...712A.141G

Context. The [Ba/Eu] abundance ratio is commonly adopted as a tracer of the relative contributions of the slow (s) and rapid (r) neutron-capture processes. However, at low metallicity ([Fe/H] ≲ −2 dex), barium can be produced efficiently by both processes, rendering [Ba/Eu] non-deterministic. We propose using the barium isotopic ratio, from the fitting of resonance Ba II line profiles affected by hyperfine splitting. This approach requires precise atomic and stellar parameters, together with advanced spectral modelling, which, so far, had remained insufficiently validated. Aims. We aim to provide a robust prescription of line-profile modelling for a reliable determination of the s- and r-process fractions of barium in ordinary and peculiar stars. These observational determinations can be used to place constraints on Galactic chemical evolution models, testing yields from different astrophysical sources. Methods. We assessed the performance of one-dimensional under local thermodynamic equilibrium (1D LTE) synthesis, 1D non-LTE synthesis, and abundance corrections based on three-dimensional model atmospheres under non-LTE (3D non-LTE) to model Ba lines. Alongside barium abundances and its isotopic ratios, we determined Eu and other neutron-capture element abundances to validate the method in the TITANSmetal-poor benchmark stars. The observational results are compared with the predictions of stochastic Galactic chemical evolution models that account for the inhomogeneous mixing in the early times. Results. We find that 1D LTE and 3D non-LTE Ba abundance determinations are equivalent, whereas the 1D non-LTE approach leads to systematic underestimations. These underestimations bias isotopic fractions towards higher r-process contributions. The inferred s- and r-process fractions demonstrate that [Ba/Eu] alone is an ambiguous tracer for ordinary stars within the −0.8 ≲ [Ba/Eu] ≲ 0 dex range. However, we identify an observational pattern in the [Ba/Eu]─[Ba/Fe] plane that can distinguish, at a given [Ba/Fe], the dominant neutron capture process. The comparison of our set of models, both for the proto-Milky Way halo and for the Gaia-Enceladus galaxy is used to put constraints on the production of Ba at low metallicity, especially evaluating the role of rotating massive stars. Conclusions. The method developed here can be applied with confidence to both ordinary stars and peculiar stars enhanced in barium.

Galaxy Cluster Detection and Dynamical Analysis in the VIPERS High-redshift Spectroscopic Survey

First Author: Abdullah, Mohamed H.
Instruments: VIMOS
ProgramIDs: 182.A-0886
BibCode: 2026ApJ..1007...36A

We present a dynamical analysis of galaxy clusters identified in the VIPERS spectroscopic survey within the redshift range 0.5 ≤ z ≤ 1.2. Cluster candidates were first detected as overdense regions in redshift space through the Finger-of-God (FoG) effect, and cluster membership was assigned using the GalWeight technique within the FoG─GalWeight methodology developed by our team. For each cluster, we derived the virial radius (R₂₀₀), velocity dispersion (σ₂₀₀), and virial mass (M₂₀₀) using the virial mass estimator. We identified 10 VIPERS clusters spanning a mass range of 0.59 × 10¹⁴ ≤ M₂₀₀/(h⁻¹M_⊙) ≤ 4.32 × 10¹⁴ and velocity dispersions of 360 ≲ σ₂₀₀ ≲ 900 km s⁻¹. We constructed a stacked rest-frame color─magnitude diagram for the cluster members and found a clear red sequence, with red galaxies more centrally concentrated than blue galaxies. As a consistency check on the recovered dynamical properties, we examined the velocity dispersion─mass relation and obtained logσ200=(2.73±0.06)+(0.36±0.18)logM200 , with an intrinsic scatter of σ_int = 0.04 ± 0.07. The recovered dynamical properties are broadly consistent with expectations from N-body and hydrodynamical simulations. We also cross-matched the VIPERS clusters with published catalogs and found at least one previously reported cluster candidate associated with each system. Overall, our results show that the FoG─GalWeight methodology, combined with the virial mass estimator, can successfully identify and characterize galaxy clusters in high-redshift spectroscopic surveys.

Spatial correlations of PAH, UV, Hα emission and IMF─PAH variations in the star-forming complexes of NGC 628

First Author: Amrutha, S.
Instruments: MUSE
ProgramIDs: 095.C-0473, 098.B-0551, 097.B-0640, 099.B-0242, 0100.B-0116, 098.C-0484, 1100.B-0651, 094.B-0321, 094.C-0623
BibCode: 2026MNRAS.551g1410A

We examine the spatial correlation of emission from polycyclic aromatic hydrocarbons (PAH) (3.3, 7.7, and 11.3

$\mathrm{\mu m}$

) with the far-ultraviolet (FUV), near-ultraviolet (NUV), and H

$\alpha$

emission from star-forming complexes (SFCs) in different regions of NGC 628. We use the James Webb Space Telescope to detect PAH emission, along with the Ultraviolet Imaging Telescope and Multi-Unit Spectroscopic Explorer observations to sample the UV and H

$\alpha$

emission, respectively. We investigate the correlation of PAH luminosities with FUV, NUV, and H

$\alpha$

luminosities for the extracted SFCs. We find that the arm and spur SFCs show bright PAH emission, except for those with only NUV emission, located primarily in bubbles and superbubbles. We also examine these correlations in the phantom void, the largest superbubble in NGC 628. We investigate the trend for FUV-NUV and the Initial mass function (IMF) index

$\alpha _2$

derived from the ratio of B stars with PAH band ratios (F335M/F1130W, F770W/F1130W, and F335M/F770W). We find that PAH band ratios increase as the IMF becomes more top-heavy and the SFCs become bluer, consistent with enhanced PAH excitation and ionization in stronger UV radiation fields. However,

$\alpha _2$

of spur SFCs shows a flat trend with PAH band ratios compared to arms. Upon closer examination, two SFCs in the shell region of the phantom void showed a flatter IMF compared to the SFC located near the elongated bubble. This is likely due to gas accumulation, possibly through feedback mechanisms in the shell region, while the SFC near the elongated bubble may have formed in a region affected by shear.

Deep MUSE observations of SNR 0509─67.5 reveal a double-degenerate merger progenitor

First Author: Das, Priyam
Instruments: MUSE
ProgramIDs: 0104.D-0104, 096.D-0352
BibCode: 2026MNRAS.550g1329D

Deep Multi Unit Spectroscopic Explorer (MUSE) observations of SNR (supernova remnant) 0509─67.5 reveal that the coronal [Fe XIV]

$\mathrm{\lambda }$

5303 emission line appears with either one or two velocity components across the entire remnant, arising from reverse-shocked ejecta moving towards and away from the observer. A supervised dense neural network classifies each spaxel and fits Gaussian profiles plus a linear function to the observed line emission. We measure a bulk Doppler velocity of

$-1000\pm 60~~\mathrm{km~s^{-1}}$

, interpreted as the line-of-sight component of the primary white dwarf's orbital velocity in a double-degenerate merger. The red- and blue-shifted ejecta map shows a flattened edge along the north-eastern rim, consistent with the companion's shadow, indicating a binary companion was present at the explosion. Modelling this feature as a cone anchored at the explosion centre and applying Bayesian inference, we recover the cone's orientation and half-opening angle. We then use the Eggleton Roche-lobe relation to infer properties of the companion. The companion was likely a

${\sim }0.6~\mathrm{M_\odot }$

white dwarf with radius

${\sim }9800$

km and orbital velocity

${\sim }1700~\mathrm{km~s^{-1}}$

at the time of explosion. Together, these results provide a complete dynamical picture of a Type Ia supernova progenitor system whose maximum-light spectrum is independently constrained by light echo observations.

High-resolution spectroscopy of Raman-scattered He II lines in the Symbiotic Nova RR Telescopii

First Author: Shin, Jaejin
Instruments: FEROS
ProgramIDs: 073.D-0724
BibCode: 2026MNRAS.550g1249S

Raman-scattered emission features in symbiotic stars provide a powerful diagnostic of mass-loss and transfer processes, as they uniquely probe both ionized and neutral regions within interacting binaries. When resolved with high-resolution spectroscopy, these features encode detailed information on the physical properties of the neutral hydrogen medium. In this work, we present high-resolution spectroscopic observations of the symbiotic nova RR Telescopii obtained with Fiber-fed Extended Range Optical Spectrograph (FEROS) in 2004 and Gemini High-resolution Optical SpecTrograph (GHOST) in 2024, providing a

$\sim$

20 yr baseline. We report the clear detection of all three Raman-scattered He II lines at 6545, 4851, and 4332 Å, and constrain the distribution and kinematics of H I through line profile analysis. The three Raman lines exhibit distinct relative velocities, indicating that they trace different depths within the H I region. The Raman conversion efficiencies of the three Raman He II lines in 2024 are significantly lower than those in 2004, indicating substantial changes in the physical properties of the neutral hydrogen region. In addition, radiative transfer modelling implies a larger covering factor (opening angle) of the neutral region in 2004 than in 2024. These results indicate that the neutral hydrogen region cannot be characterized by a single H I column density, emphasizing the need for advanced radiative transfer modelling that accounts for the complex kinematics and geometry of the H I region. Overall, these results establish Raman-scattered He II lines as a powerful tool for spectroscopic tomography, allowing for direct constraints on the structure and kinematics of neutral hydrogen in symbiotic binaries.

Oxygen in the protostellar clump OMC-2 FIR4

First Author: Harju, J.
Instruments: nFLASH
ProgramIDs: 0105.C-0281
BibCode: 2026A&A...712A..21H

Context. Atomic oxygen (O I), OH, H₂O, and CO are the main carriers of oxygen in dense interstellar gas. The far-infrared lines of these species are considered important coolants of the shock-heated dense gas associated with protostellar outflows. Their relative abundances depend on the nature of the shock and usually remain uncertain in observational studies. Aims. We determined the relative abundances of O I, OH, H₂O, and CO in the warm inner parts of the protostellar clump OMC-2 FIR4 in Orion A. The clump contains several young stellar objects. Methods. The upGREAT receiver, which includes the High Frequency Array (HFA; operating at 4.74 THz, λ = 63 µm), on board the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA) was used to observe OMC-2 FIR4 in the O I, OH, OD, HDO, and CO lines. Additional HDO lines were observed with the Atacama Pathfinder Experiment (APEX). Archival H₂O and CO spectra observed by the Herschel satellite were included in the analysis. The observed lines were reasonably well reproduced by an expanding spherical shell model. Results. The O I spectrum at 63 µm towards OMC-2 FIR4 is dominated by a broad line component, on top of which medium-wide and narrow line components can be discerned. The same components are present in the OH, H₂O, and high-J CO spectra towards this source. We find that O I is more abundant than H₂O in the shocked gas. In the broad line component, the following abundance ratios are derived: O I/H₂O ∼ 700, O I/OH ∼300, and O I/CO ∼4. The high relative abundance of atomic oxygen there suggests an origin in dissociative J-shocks that are associated with strong ultraviolet radiation. The O I/CO ratio decreases below unity in the components with a smaller velocity dispersion, and these components also have higher abundances of H₂O than the broad line component, although they remain below that of CO. The HDO/H₂O ratio in the low-velocity components corresponds to the average ratio in the icy mantles of dust grains, and the presence of water there could also be understood in terms of sublimation without invoking high-temperature chemistry.

Chemical composition and kinematics of ionised gas in low-mass star-forming galaxies with extremely high [O III]/[O II] ratios

First Author: Izotov, Y. I.
Instruments: XSHOOTER
ProgramIDs: 105.20LV
BibCode: 2026A&A...712A..19I

We present Very Large Telescope/Xshooter spectrophotometric observations of eleven low-redshift (z < 0.085) compact star-forming galaxies (the 'high O₃₂ sample'). These galaxies are characterised by extremely high emission-line ratios, [O III]λ5007/[O II]λ3727, ranging from 11 to 42. Galaxies with such high ratios are promising candidates for leaking large amounts of Lyman continuum radiation. They are characterised by low oxygen abundances, 12 + log(O/H) = 7.5 − 8.0, and low stellar masses, M_★ ∼ 10⁶ − 10⁸ M_⊙. We used strong emission lines of various ions in all spectra to derive helium and oxygen abundances and N/O, Ne/O, S/O, Cl/O, Ar/O, and Fe/O abundance ratios. We also derived macroscopic velocity dispersions, σ(λ), from various emission lines of different ions. We find that σ(4861) of the Hβ emission line increases with increasing stellar mass and decreasing O₃₂ ratio. In contrast, σ(λ)/σ(4861) ratios for various lines are close to unity. Exceptions are the σ(λ)/σ(4861) of two lines, He II 4686 and He I 10830, which are considerably higher than unity, and those of four lines, [O II] 3726, 3729, [S II] 6717, and 6731, for which σ(λ)/σ(4861) is lower than unity. The He II 4686 and He I 10830 lines are likely produced in the inner parts of H II regions and are broadened by dynamical processes generated by massive stars, and, in the case of the He I 10830 emission line, by radiative scattering. Emission in the [O II] and [S II] lines is produced mainly in the outer and likely more quieter parts of H II regions. ★ Based on observations collected at the European Southern Observatory under ESO programme 0105.B-0772(A).

Berkeley 32: A Metal-poor and Dynamically Evolved Open Cluster with Evidence of Radial Migration

First Author: Cinar, D. C.
Instruments: FLAMES, GIRAFFE, UVES
ProgramIDs: 087.D-0203, 087.D-0230, 087.D-0276, 088.B-0403, 088.B-0492, 088.C-0239, 088.D-0026, 088.D-0045, 089.D-0038, 089.D-0298, 089.D-0579, 090.D-0487, 091.D-0427, 092.D-0171, 092.D-0477, 093.D-0286, 093.D-0818, 094.D-0363, 094.D-0455, 171.D-0237, 187.B-0909, 188.B-3002, 193.B-0936, 193.D-0232, 197.B-1074, 278.D-5027, 292.D-5043, 381.C-0270, 383.D-0412, 383.D-0594, 386.B-0009, 60.A-9143, 60.A-9800, 71.B-0414, 71.D-0065, 71.D-0127, 71.D-0205, 072.D-0019, 072.D-0309, 072.D-0337, 072.D-0406, 072.D-0507, 072.D-0742, 072.D-0777, 073.C-0251, 073.D-0100, 073.D-0211, 073.D-0550, 073.D-0695, 073.D-0760, 074.D-0571, 075.C-0245, 075.C-0256, 075.D-0492, 076.B-0263, 076.D-0220, 077.C-0655, 077.D-0246, 077.D-0484, 078.D-0825, 079.B-0721, 079.D-0178, 079.D-0645, 079.D-0674, 079.D-0825, 080.B-0489, 080.B-0784, 080.C-0718, 081.D-0253, 081.D-0287, 082.D-0726, 083.B-0083, 083.D-0208, 083.D-0671, 083.D-0682, 083.D-0798, 084.D-0470, 084.D-0693, 084.D-0933, 085.D-0205, 086.D-0141
BibCode: 2026AJ....172..140C

We present a comprehensive chemodynamical analysis of the old, metal-poor open cluster Berkeley 32 based on Gaia DR3 astrometry and Gaia-ESO Survey DR5.1 spectroscopy. Cluster membership is determined using a Gaussian mixture model applied to proper-motion components and trigonometric parallaxes. Isochrone fitting yields an age of 4.9 ± 0.5 Gyr, a heliocentric distance of 3325 pc, and an extinction of A_V = 0.38 ± 0.12 mag. Spectroscopic member stars exhibit a mean metallicity of [Fe/H] = −0.39 ± 0.02 dex, near-solar α-element abundances, and a weighted mean radial velocity of V_rad = 106.26 ± 0.03 km s⁻¹. The [Y/Mg] chemical clock yields an age of 4.73 ± 2.39 Gyr, consistent with the isochrone estimate. Orbital integration indicates a moderately eccentric orbit (e = 0.268 ± 0.004) with a guiding radius of R_g = 8.82 kpc. The inferred chemical birth radius, R_b = 9.82 kpc, together with ∆R ≍ − 1 kpc, suggests moderate inward radial migration, while the offsets among R_b, R_g, and R_GC are consistent with both churning and blurring processes. A photometric analysis identifies a binary fraction of f_b = 0.449 ± 0.017 for systems with mass ratios q ≥ 0.5, implying a substantial unresolved binary population. Radial cumulative distribution functions further reveal significant mass segregation, with evolved stars more centrally concentrated than main-sequence stars. These results indicate that Berkeley 32 is a dynamically evolved old-disk cluster whose present-day structure and orbit preserve signatures of both internal dynamical evolution and radial migration within the Galactic disk.

I can do it with a broken planetesimal: characterizing the planetary debris in heavily polluted cool white dwarfs

First Author: Cutolo, Anna-Maria
Instruments: XSHOOTER
ProgramIDs: 0101.C-0646, 093.C-0275, 1103.D-0763
BibCode: 2026MNRAS.551g1349C

We present the analysis of four cool and strongly metal-polluted H-atmosphere (DAZ) white dwarfs observed with X-shooter. We compared their atmospheric parameters obtained from spectroscopy, photometry, and a hybrid method, finding a difference of up to

${\simeq} 160\,$

K in

$T_\mathrm{eff}$

, and

${\simeq} 0.3$

dex in

$\log g$

, between the three analyses. We adopt the

$T_\mathrm{eff}$

and

$\log g$

from the photometric analysis, and subsequently measured the metal abundances of the photospheric elements from spectroscopic modelling, analysing their compositions. We identified from five to eleven unique metals in the photospheres of the four white dwarfs, with total accretion rates ranging from

$10^{8}$

$10^{9}$

$\mathrm{g~s^{-1}}$

. The compositional analysis of WD J035826.49+215726.16 suggests an accreted planetesimal akin to a core-rich differentiated body, with a core mass fraction of 70 per cent, placing it among the most core-rich objects known to be accreted by white dwarfs. The parent body accreted by WD J042643.98─415341.44 shows an enhancement in Na compared to that of the Earth, making it most similar to primitive chondrites. The photosphere of WD J013222.88+052923.71 is greatly depleted in core-like material, and its composition resembles that of pure crust/mantle material. WD J232428.21─021643.65 has accreted the most Fe-rich planetesimal, with an Fe mass fraction of 67 per cent. We compare these results to other published studies and conclude that these white dwarfs are among the most heavily polluted cool DAZs studied to date, increasing the sample of cool H-dominated white dwarfs with five or more metals by 50 per cent.

Discovery of the λ Bootis phenomenon in an early B-type star

First Author: Olbermann, J.
Instruments: FEROS
ProgramIDs: 088.D-0064
BibCode: 2026A&A...712A..68O

Context. Chemically peculiar A-type stars of the λ Boo class are characterised by depletions of refractory elements and normal volatile species. Their formation channel(s) have not yet been fully established, but they provide insight into star-disc-planet interactions during star formation, star-planet interactions in later system evolution, or interactions between stars and the interstellar medium. Aims. We report the first detection of the λ Boo phenomenon in a massive early B-type star, HD 37356, a member of Ori OB1c. Methods. We analysed a high-quality spectrum using a hybrid non-LTE model-atmosphere technique. We determined atmospheric parameters and elemental abundances using neural networks to emulate synthetic spectra, coupled with a Markov chain Monte Carlo algorithm. We also derived the fundamental parameters of the star using Gaia data and stellar evolution models. Results. HD 37356 closely resembles the Morgan-Keenan standard γ Peg, closely agreeing in spectral signatures except for the lines of refractory elements, which are systematically weaker. The quantitative analysis yields similar stellar parameters. The abundances of volatile elements are compatible with cosmic standard abundances, while refractory species are depleted by 0.25─0.45 dex. In particular, the lower iron abundance explains the different pulsational behaviour of HD 37356 compared to γ Peg. Of the different formation channels for λ Boo stars, only the accretion of gas depleted in refractory elements from the circumstellar disc during star formation appears to be feasible in this case. This scenario requires HD 37356 to be a true slow rotator in order to prevent the abundance pattern from being erased by internal mixing processes such as meridional circulation.

Revealing the High-redshift Host Galaxy of the Short GRB 061201 with JWST

First Author: Mao, Yuhan
Instruments: FORS2
ProgramIDs: 177.A-0591, 078.D-0809, 079.D-0909
BibCode: 2026ApJ..1007...14M

Using deep near-infrared and optical JWST and Hubble Space Telescope imaging, we identify a new host-galaxy candidate for the short GRB 061201 at an angular offset of ∼2″ from the optical afterglow, with a best-fit photometric redshift of z ∼ 1.2. We compare it with the prior putative host candidate at z = 0.111. The new candidate has a chance-coincidence probability of P_cc = 0.18, above the classical 0.1 threshold but consistent with a physical association given the depth of the JWST imaging. In contrast, the lower P_cc = 0.11 of the z = 0.111 galaxy is driven primarily by bright-tail statistics. A high-redshift origin is favored by three lines of evidence. First, although both scenarios satisfy the Amati (E_p,i─E_iso) relation, the beaming-corrected energy at z = 0.111 makes GRB 061201 an outlier in the Ghirlanda (E_p,i─E_γ) relation. Second, near-infrared data disfavor an AT2017gfo-like kilonova at z = 0.111. Third, afterglow modeling favors the high-redshift scenario, with the Akaike information criterion (AIC) for the z = 1.2 model lower than that for z = 0.111 by ∆AIC = 16.35. Adopting the z ∼ 1.2 candidate as the host gives a physical offset of 16.4─16.9 kpc (substantially reduced from ∼42 kpc implied under the low-redshift scenario) and a stellar age of ∼2 Gyr, consistent with the general population of short gamma-ray bursts (sGRBs). Furthermore, a low-redshift origin implies a binary neutron-star merger rate of ∼1400 Gpc⁻³ yr⁻¹, in tension with gravitational-wave constraints. We conclude that a moderately high-redshift host provides a more self-consistent physical framework for GRB 061201, demonstrating the capability of deep JWST imaging for historically hostless sGRBs.

Southern Massive Stars at High Angular Resolution (SMaSH+): Properties of hierarchical massive triples

First Author: Bordier, E.
Instruments: NACO, PIONIER
ProgramIDs: 189.C-0644
BibCode: 2026A&A...712A..53B

Context. While massive stars are frequently found in triple architectures, the lack of observed parameter distributions has long remained a bottleneck for statistical models of their evolution. Aims. We bridge this gap by compiling the first representative set of physical and orbital distributions for main-sequence hierarchical massive triples. Methods. We present a homogeneous analysis of 26 O-type hierarchical triples identified in the SMaSH+ survey by combining spectroscopic data for inner binaries with interferometric and aperture masking detections of tertiary companions within ∼200 au. We derive the distributions of masses, mass ratios, and separations, and investigate their joint probability density functions. We assess the dynamical stability of these systems. We estimate the relative importance of secular processes by comparing the von Zeipel─Kozai─Lidov (ZKL) timescale to the general relativistic precession timescale for several systems with well-constrained orbital solutions. Finally, we evaluate the observational completeness and find no substantial detection bias for separations ≲100 au and mass ratios q_out > 0.1. Results. The sample is dominated by strongly hierarchical configurations, consisting primarily of tight inner spectroscopic binaries (a_in < 1 au) and wider tertiaries ( a∼_out/a_in > 70 a ∼ out a in > 70 for most systems). We find no significant correlation between tertiary mass and either inner-binary mass or outer separation, indicating a broad diversity of system architectures. Ten systems (out of 26) host relatively massive tertiaries (q_out > 0.5), especially at closer outer separations ( a∼_out ≲ 30 a ∼ out ≲ 30 au). For two to four systems out of five with well-constrained orbits, general relativistic precession dominates over ZKL oscillations in their current configuration, although ZKL-driven migration may have contributed to the formation of the observed short-period inner binaries. These results provide the first observationally grounded distributions of key parameters for massive hierarchical triples and offer important constraints for population synthesis and evolutionary models, particularly regarding the role of tertiary companions in shaping binary evolution. ★ Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 189.C-0644.

The complex history of NGC 1427A revealed by its star clusters and star formation history

First Author: Fahrion, Katja
Instruments: MUSE
ProgramIDs: 110.23VM, 094.B-0612
BibCode: 2026A&A...712A..28F

Star-forming low-mass galaxies in the dense environments of galaxy clusters provide opportunities to study how environmental effects such as ram-pressure stripping, tidal interactions, or galaxy mergers shape a galaxy's star formation history. We combined integral-field spectroscopic observations with the Multi Unit Spectroscopic Explorer (MUSE) and available multi-band imaging of the star-forming galaxy NGC 1427A, located near the centre of the Fornax galaxy cluster, at a distance of 20 Mpc. Our aim was to trace the evolutionary history of NGC 1427A using the star formation history reconstructed from the integrated spectra and employing star clusters as surviving tracers of past star formation episodes. We fitted the spectral energy distribution of 222 star cluster candidates using archival u, g, r, and i photometry to derive the ages and masses. For 58 clusters, we additionally incorporated their MUSE spectra in the fits and found an encouraging agreement between the photometric and spectroscopic results. The comparison of the age distribution of star clusters with star formation histories from a full spectrum fitting of the MUSE data found a reasonable agreement, with evidence for multiple episodes of star formation throughout the history of NGC 1427A. In particular, we found a population of young clusters (~10 Myr) that is located along the star formation edge and within the northern object, and a population of intermediate-age clusters (~100─300 Myr) with corresponding peaks in the star formation history of NGC 1427A. We interpret these populations in the context of the orbital evolution of NGC 1427A in the Fornax cluster and conclude that this galaxy has experienced not only ram-pressure stripping, but also tidal interactions or even a minor galaxy merger. The northern object is likely a regular component of the galaxy.

A Supermassive Black Hole Mass Measurement in NGC 5102 with Schwarzschild Orbit-superposition Modeling

First Author: Waters, Thomas K.
Instruments: MUSE
ProgramIDs: 60.A-9308, DataDoiProID
BibCode: 2026ApJ..1007...63W

We present a stellar-dynamical mass measurement of the central black hole in the lenticular galaxy NGC 5102 (SA0⁻). Our analysis combines high-quality integral-field spectroscopy from the Very Large Telescope Multi Unit Spectroscopic Explorer with high-spatial- and high-spectral-resolution Hubble Space Telescope Imaging Spectrograph observations, using the Ca II triplet as a stellar kinematic tracer. We constrain the black hole mass with axisymmetric, three-integral Schwarzschild orbit-superposition models, incorporating surface-brightness measurements from Hubble Space Telescope F547M WFPC2 imaging. Assuming a distance of 3.66 Mpc, we find a black hole mass of (1.30−0.18+0.19)×106M⊙ , which is within 1.7σ of a previous CO band-head-based Jeans anisotropic modeling result ( M∙=(9.1−1.5+1.8)×105M⊙ ). Our measurement is also consistent with literature extrapolations of the M_∙─σ_e relation into the currently undersampled low-mass regime. The close agreement between these independent dynamical approaches provides external validation of the Jeans anisotropic modeling framework and supports the robustness of our Schwarzschild orbit-superposition result, bolstering confidence in future black hole mass measurements with this framework.

Tidal preconditioning and ram-pressure stripping in NGC 1427A: Deep VLT/MUSE spectroscopy and FUV-to-radio observations trace a Fornax cluster dwarf in transformation

First Author: Carvajal, J. P.
Instruments: MUSE
ProgramIDs: 094.B-0612, 110.23VM, 111.24R5, DataDoiProID
BibCode: 2026A&A...712A..29C

Context. The early environmental transformation of low-mass cluster galaxies from gas rich to gas poor remains poorly constrained in part because clear phase-resolved observations are rare. NGC 1427A, a disturbed star-forming dwarf in the Fornax cluster, offers a favorable case for studying this process. Aims. We aim to build a spatially resolved multiphase picture of NGC 1427A in order to constrain the roles of ram-pressure stripping and tidal perturbations in its present transformation. Methods. We combined a deep, spatially contiguous VLT/MUSE mosaic with ancillary data from the far ultraviolet to the radio. Full-spectrum fitting of the MUSE cube yielded maps of stellar kinematics, ages, metallicities, and continuum attenuation, while emission-line modeling provides ionized-gas kinematics, Balmer-decrement reddening, and star formation rate surface densities. The ancillary multiwavelength data trace the neutral and molecular gas, dust, and recent star formation, placing the MUSE-based results in a broader multiphase context. Results. We find a pronounced decoupling between stars and gas: The H I and ionized gas rotate about an axis tilted with respect to the stellar field and are globally blueshifted. Joint constraints from stellar and nebular attenuation, infrared dust tracers, and H I morphology indicate stripping with a strong line-of-sight component that has progressed into the interstellar medium. At the same time, the asymmetric distribution of gas and dust, together with the structured and time-dependent star formation, points to an additional gravitational perturbation, with a recent mild flyby by a nearby dwarf being the favored interpretation. Conclusions. We propose that dwarf─dwarf tidal effects have torqued and preconditioned the gas, while the Fornax intracluster medium is driving ram-pressure stripping that now reaches the interstellar medium and coincides with a declining global star formation rate. This places NGC 1427A at the onset of environmentally driven quenching, making it a useful benchmark for early cluster dwarf transformation.

An Ultramassive White Dwarf with a Likely Oxygen─Neon Core

First Author: Arseneau, Stefan M.
Instruments: UVES
ProgramIDs: 108.22CP, 115.28D4
BibCode: 2026ApJ..1006..217A

The core composition of ultramassive white dwarfs remains an open question in stellar evolution. The C content of white dwarf cores is critical to their role as progenitors of Type Ia supernovae. However, because the stellar photosphere only extends to the outermost layer of the star, observational probes of core compositions are limited. Here we present gravitational redshift measurements of an ultramassive white dwarf, SDSS J060851.44-005950.3, which indicate the likely presence of an O/Ne core. We measure the mass ( 1.226−0.025+0.024M⊙ ) and radius ( 0.491−0.009+0.009R⊕ ) of the white dwarf using gravitational redshifts from high-resolution Ultraviolet and Visual Eschelle Spectrograph and MagE spectra paired with independent constraints from photometry. By comparing to state-of-the-art mass─radius relations for ultramassive white dwarfs, we find preference for an O/Ne core over a C/O core, with a Bayes factor of 2.7. This is a white dwarf that is likely structurally incapable of producing a Type Ia supernova, according to current understanding of supernova physics. This object provides evidence that white dwarfs that pass through the Q-branch without experiencing a delay in cooling compared to the normal white dwarf cooling sequence likely have O/Ne cores.

Multi-epoch scattered-light analysis of HD 135344B: New evidence for a spiral-driving protoplanet

First Author: Latour, J.
Instruments: ERIS, NACO, SPHERE
ProgramIDs: 111.24HH, 109.23HK, 0101.C-0924, 095.C-0298, 2100.C-5045, 099.C-0883, 090.C-0443, 113.26B2
BibCode: 2026A&A...711A.292L

Context. The HD 135344B (SAO 206462) disk exhibits strong signposts of planet formation both in scattered light and submillimeter continuum images. ALMA images in the submillimeter revealed a gap-crossing dust filament whose position coincides with a twist detected in the scattered-light spiral structure. Analysis of the spiral dynamics in polarized light also hints at a spiral-driving protoplanet in the submillimeter gap. Aims. We aim to study the overall dynamics of the three spirals in the disk, as well as the motion of the twist over a 10-year baseline, at different IR wavelengths. We also seek to assess the authenticity of a candidate protoplanet recently claimed in the disk. Methods. We used high-fidelity postprocessing algorithms such as iterative principal component analysis to minimize the biases induced by angular differential imaging on extended sources and conduct a thorough analysis of archival VLT/NACO, VLT/SPHERE, and VLT/ERIS datasets in order to obtain the spiral traces and measure their orbital motion in multiple wavelength bands in scattered light. We also reprocessed archival JWST/NIRCam datasets with these algorithms. Results. We measured an average spiral orbital motion of 0°.81 ± 0°.05 yr⁻¹, in agreement with the literature value of about 0°.85 yr⁻¹ at all wavelengths. With simple modeling of the twist morphology, we confirm that it is indeed co-moving with the spiral in which it is embedded. While the position angle of the twist coincides with the dust filament, it is located at a smaller angular separation from the star, which we attribute to the fact that the spiral trace moves away from the central star with increasing wavelength. We find that a previously claimed protoplanet candidate in the disk can be adequately explained as a postprocessing artifact. Conclusions. Our confirmation that the motion of the scattered light twist is consistent with the orbital velocity of a planet at 69 ± 4 au over a 10-year baseline suggests that the spirals, the gap, and the dust filament in the submillimeter continuum, as well as the twist in scattered light, could indeed all be attributed to the same hypothetical protoplanet deeply embedded within the spiral. A perplexing trend for a wavelength-dependence of the angular distance of the spiral traces to the central star still remains to be explained.

VLTI-GRAVITY measurements of cool evolved stars: II. Pulsation properties and mass-loss process of the Mira star R Car and the red supergiant VX Sgr

First Author: Jadlovsky, Daniel
Instruments: GRAVITY
ProgramIDs: 105.207Y, 0103.D-0245, 115.27VK, 0102.D-0197, 0101.D-0616, 0100.D-0835
BibCode: 2026A&A...711A.259J

Aims. The mass-loss process of red supergiant (RSG) and asymptotic giant branch (AGB) stars and its relation to variability are poorly constrained. We aim to study the photosphere and near-surface atmospheric structure, where the mass-loss is initiated. For this purpose, we studied two oxygen-rich evolved stars: the Mira-type AGB star R Car and the RSG VX Sgr. Methods. We used the VLTI-GRAVITY instrument operating in the near-infrared K-band. Our sample comprises 54 VLTI-GRAVITY snapshots (18 R Car, 36 VX Sgr) taken over about 7 years, making it the largest VLTI time series dataset to date. We determined the angular diameter as a function of time for the continuum (photosphere) and selected atomic and molecular bands, i.e., lines of Ti I and Sc I as well as bands of H₂O and CO. Furthermore, we compared the variability and atmospheric structure to state-of-the-art radiative-hydrodynamics CO5BOLD 3D simulations. Results. The radii of photosphere (R_⋆) and extended atmospheric layers are variable and relate to the light curve with phase shifts. The near-photospheric layers show a maximum radius near visual brightness minima (φ_vis ∼ 0.4─0.6). Inner atomic (Ti I, Sc I) and molecular (H₂O) layers are further phase-shifted by ∆φ_vis ~ 0.05. The more extended CO layers show longer, irregular periods and maximum extensions of ∼1.3─1.7 R_⋆ for R Car and of ∼1.5─2.2 R_⋆ for VX Sgr. Comparison with synthetic interferometric data of an AGB model based on several pulsation cycles in CO5BOLD simulations revealed a similar behavior. The photosphere shows regular pulsations, but with maximum diameters preceding minimum brightness (φ_vis < 0.5). The H₂O layer showed a much weaker extension compared to our observations, while CO showed a good agreement. Furthermore, during the 2020─2021 season, VX Sgr exhibited an extreme mass-loss event similar to that of Betelgeuse, preceded by two strong shocks and culminating with the extreme expansion of H₂O and CO layers, both up to ∼2.2 R_⋆. Unexpectedly, during this event, we also detected Brackett γ in interferometric data as well as strong Balmer emission in optical spectra, both of which are also signatures of a shock propagating through the atmosphere. Conclusions. The Mira R Car showed an estimated photospheric radius of R_⋆ = 280 ± 25 R_⊙, with a regular fundamental mode (FM) pulsation amplitude of ∼13% of R_⋆. During its active cycle, the extreme RSG VX Sgr showed R_⋆ = 1556 ± 110 R_e, with an FM pulsation amplitude of ∼13% of R_⋆, the same as R Car. During its quiescent cycle, it showed a smaller value, R_⋆ = 1456 ± 108 R_⊙, and low-amplitude pulsations near the first overtone (O1), only ∼4% of R_⋆. This supports a steady mass-loss process for Mira stars related to stable large-amplitude FM pulsation, whereas the mass-loss process for RSGs may be dominated by extreme events connected to changes in the pulsation mode from low-amplitude O1 to large-amplitude FM pulsations.

Optical outburst evolution of the transient black hole X-ray binary Swift J1727.8−1613: disc response to jet ejections and late-outburst emergence of powerful disc winds

First Author: Castro Segura, N.
Instruments: XSHOOTER
ProgramIDs: 112.26W7, 111.265Y
BibCode: 2026MNRAS.550g1175C

Swift J1727.8─1613 is a newly discovered transient low-mass X-ray binary harbouring a stellar-mass (

$\sim 10\,\mathrm{ M}_\odot$

) black hole. We present state-resolved VLT/X-Shooter optical spectroscopy of its 2023 outburst, sampling the luminous hard-to-soft and late soft-to-hard transitions. During the onset of the brightest radio flare, He II flux rises relative to adjacent epochs, with reduced peak-to-peak separation and full-width-half-maximum, consistent with enhanced irradiation shifting line emissivity to larger radii. We detect no contemporaneous change in the line base tracing the inner disc. The most dramatic change occurs at the onset of the dim-hard state, when strong, broad (higher-order) Balmer lines appear in absorption, and He II remains in emission, but becomes highly asymmetric. While the hardening of the X-ray spectrum likely promotes the reappearance of an underlying disc photosphere, the kinematic alignment between the Balmer absorption (

$v_w\sim -750\, \mathrm{km\, s^{-1}}$

) and the suppressed blue peak of He II suggests a unified origin in a massive, cool (

$T\lesssim 10^{4}\, \mathrm{K}$

) accretion disc wind. Radiative transfer simulations demonstrate that such asymmetric He II profiles are naturally produced in a rotating and accelerating outflow. Using the Sobolev approximation, we estimate the wind mass-loss rate to be

$\dot{M}_w\gtrsim 10^{-9}\, \mathrm{ M}_\odot \, \mathrm{yr^{-1}}$

, comparable to the instantaneous accretion rate and a significant fraction of the secular mass-transfer rate from the donor. If persistent at quiescent-level X-ray luminosities, this outflow could strongly impact the system's secular evolution.

Discovery of a star sensitive to the spin of Sagittarius A*

First Author: Abd El Dayem, K.
Instruments: GRAVITY
ProgramIDs: 60.A-9102, 105.20B2, 112.25CV, 114.270V, 111.24H1, 113.268P, 115.27WT
BibCode: 2026Natur.657..359A

Residing in the centre of the Milky Way, Sagittarius A* (Sgr A*) is the closest massive black hole¹ (MBH). Its vicinity has allowed measuring individual stellar orbits around it^{2, 3--4}. The stars act as test particles and probe the gravitational potential around the 4.3 × 10⁶M_⊙ MBH. These observations have determined the central mass to sub-per-cent precision⁵, and the mildly relativistic motions of stars have given access to the dominant relativistic corrections, the gravitational redshift^6,7, the transverse Doppler effect and the prograde precession imposed by the Schwarzschild metric nature of the potential⁸. These effects are of order β² = (v/c)² (for velocity v and speed of light c). The Kerr metric for a rotating black hole leads to corrections of order β³. Here, we report the discovery of a faint main-sequence star (m_K = 19.3), S301, on an 8.7-year orbit and with small enough a pericentre distance, such that the peak velocity of the star reaches 25,000 km s^-1. Within the measurement abilities of current near-infrared interferometry and future spectroscopy on an extremely large telescope, the motion of S301 is directly sensitive to the spin of Sgr A*. The high eccentricity of S301 suggests that it is the captured component of a binary that was torn apart by the Hills mechanism.

Chemical Abundances Shape History (CASH). I. A Link between Giant Planets' Orbital Periods and Host Stellar C/O Ratios

First Author: Zhang, Ruisheng
Instruments: HARPS
ProgramIDs: 072.C-0488, 085.C-0063, 082.C-0212
BibCode: 2026AJ....171..302Z

The chemical abundance of host stars plays a pivotal role in shaping the formation history of planetary systems, yet the influence of elements beyond iron remains poorly understood. Here, we investigate the relationship between the carbon-to-oxygen (C/O) ratio of host stars and the orbital periods of giant planets. By analyzing high-resolution spectroscopic data from 598 planet-hosting stars (hosting 929 planets) across the Sloan Digital Sky Survey, Keck, and HARPS surveys, we identify a correlation; stars with higher C/O ratios are more likely to host longer-period giant planets. Theoretical models of pebble-driven planet formation and migration further support this observation, demonstrating that elevated C/O ratios enhance solid material availability at outer disk regions, promoting giant planet formation at larger distances and subsequent moderate inward migration. Our findings establish stellar C/O as a critical factor in shaping the orbital architecture of giant planets, bridging disk chemistry to planetary system evolution.

Exploring the surface of HD 189733 via Doppler shadow analysis of planetary transits

First Author: Gonçalves, E. C.
Instruments: ESPRESSO
ProgramIDs: 1104.C-0350
BibCode: 2026A&A...709A..16G

Context. Transmission spectroscopy has advanced our understanding of exoplanet atmospheres, but it can be hindered by contamination originating in stellar heterogeneities, mainly coming from line-of-sight effects. Therefore, probing how stellar spectra vary across the stellar surface is essential to accurately disentangling stellar and planetary spectral contributions in transit observations. Such observations can actually be used to reconstruct the local stellar spectra behind the planet's transit chord. These methodologies can help us learn more about the physics of stellar surface and how to tackle line-of-sight effects. Aims. In this paper, we study the centre-to-limb variations of line profiles across the surface of HD 189733 using the ESPRESSO spectrograph. We build on other works by analysing the same sets of Fe I lines, allowing for a direct comparison of results and an assessment of the feasibility of applying the Doppler shadow technique with ESPRESSO. We gain a better understanding of the variations in line profiles, while also making a comparison between the data of HD 189733 and synthetic spectra and solar data. Methods. We analysed spectra collected by ESPRESSO during two transits of HD 189733 b as separate sets of data. We performed a cross-correlation of each individual spectrum with two different masks made of selected Fe I spectral lines for a total of four sets of cross-correlation functions (CCFs) and employed a Doppler shadow methodology to retrieve profiles for local regions of the stellar surface. We then compared the results with previous works and with solar disc-resolved observations from IAG ATLAS. Finally, we compared the data with two separate transit simulations made using SOAPv4 with Turbospectrum synthetic spectra computed with MARCS stellar atmosphere models under local thermal equilibrium (LTE) and non-LTE (NLTE) conditions. Results. For the profile depth of three sets of Fe I CCFs, we verified a statistically significant increase in line depth from the stellar limb to the centre. This variation was expected from simulations with MARCS models, although the solar data present a smaller gradient in the variation of line depth. In the case of the width of the line profiles, we verified that the profile width decreases from stellar limb to stellar centre for a set of Fe I CCFs. This result is consistent with the behaviour observed in solar data, but not reproduced by the simulations. Conclusions. These results highlight the abilities of ESPRESSO in providing the necessary precision and resolution to study centre-to-limb variations of spectral line profiles on the surface of other stars with the use of CCFs. The local CCF profiles of HD 189733 agree with the IAG ATLAS data, but disagree with simulations on line widths, indicating that important physical processes are missing and must be included to recover accurate profile widths.

ALMA High-J CO Spectroscopy of High-redshift Galaxies. I. An Archive-based Catalog of CO Spectral Line Energy Distributions

First Author: Tadaki, Ken-ichi
Instruments: ALMA_Band_3, ALMA_Band_4, ALMA_Band_5, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2017.1.00963.S, 2016.1.00330.S, 2012.1.00844.S, 2022.1.00353.S, 2021.1.00168.S, 2021.1.01015.S, 2017.A.00032.S, 2015.1.00928.S, 2021.1.01313.S, 2023.1.01532.S, 2018.1.00081.S, 2017.1.01516.S, 2018.1.00966.S, 2019.1.00533.S, 2022.1.00346.S, 2018.1.00861.S, 2015.1.00504.S, 2015.1.01042.S, 2023.1.00852.S, 2023.1.00653.S, 2019.1.00466.S, 2019.1.00147.S, 2019.1.00080.S, 2023.1.01281.S
BibCode: 2026ApJS..286...11T

High-J CO emission in high-redshift galaxies has been studied primarily on an individual-source basis, limiting our ability to draw population-level conclusions about molecular-gas excitation. To address this limitation, we present a catalog of CO spectroscopy based on archival data from the Atacama Large Millimeter/submillimeter Array (ALMA) for a sample of galaxies at z > 3, focusing on high-J transitions (J_up = 9─17). Combining ALMA archival data with published measurements, we compile CO spectral line energy distributions (SLEDs) for 38 well-studied systems spanning z ≃ 3.1─6.9, including five hot dust-obscured galaxies (Hot DOGs), 17 submillimeter-bright galaxies (SMGs), and 16 optically selected quasars. The class-median SLEDs rise steeply to J_up = 9 and remain approximately flat through J_up ∼ 11─12. SMGs show relatively stronger low- to mid-J emission relative to CO J = 9─8, while Hot DOGs exhibit tentative evidence for higher excitation. Comparison with simple excitation models suggests that X-ray-dominated region (XDR) heating or dense, shock-heated gas can account for the extended high-J CO SLEDs. A tentative anticorrelation between the CO(9─8)-to-infrared luminosity ratio and excitation among the dusty galaxy populations suggests that the enhanced excitation in Hot DOGs may be driven by XDR heating from the activity of an obscured active galactic nucleus rather than by shocks. Because the sample is restricted to sources with detected high-J CO lines, it is biased toward highly excited systems. It nonetheless provides a reference for designing future systematic surveys of high-J CO emission with a statistically complete or flux-limited sample.

Super-Jeans Fragmentation and Supply-limited Accretion: Environment-dependent Coevolution of Low- and High-mass Cores

First Author: Miao, Dan
Instruments: ALMA_Band_6
ProgramIDs: 2018.1.00192.S, 2015.1.01539.S, 2017.1.00716.S
BibCode: 2026ApJ..1007..204M

Protostellar core formation and growth in high-mass star-forming regions remain key to understanding massive star birth. We analyze the masses of 839 cores (resolved at scales of a few thousand au) from the ASHES project targeting 39 massive infrared dark cloud clumps. The masses of the three most massive cores scale linearly with the total core mass. They maintain respective constant mass fractions of ~25%, 16%, and 10% along the mass-growth sequence. These fractions reveal that the progenitor seeds destined to become high-mass cores establish their mass dominance very early. Additionally, the Gini coefficient (a statistical measure of inequality) of the core mass distributions increases along the mass-growth sequence, confirming that the relative population of low-mass cores builds up toward later stages. This points to an environment-dependent fragmentation picture: central prestellar seeds rapidly evolve into high-mass cores via transport-driven super-Jeans fragmentation under rapid, nonstationary mass accumulation in high-density, turbulent hubs, and subsequently maintain their dominance through supply-limited synchronized growth (at R < 1 pc, nH2>105cm-3 ), while the formation of the surrounding low-mass cores is relatively delayed due to their lower gas densities and the lack of nonstationary inflow acceleration effect, resulting in their continuous emergence through Jeans-like fragmentation in lower-density envelopes. This picture is consistent with a gravity-driven scenario where the local freefall time is the controlling factor. Our analysis suggests that nonstationary density-regulated fragmentation and supply-limited accretion jointly drive the synchronized coevolution of the core cluster, seamlessly linking small-scale core growth with large-scale reservoir regulation.

Revealing the nature of the starburst galaxies in the z = 2.4 overdensity HATLAS J0849

First Author: Kaasinen, Melanie
Instruments: ALMA_Band_4
ProgramIDs: 2023.1.00714.S, 2018.1.01146.S
BibCode: 2026MNRAS.551g1444K

Today's most massive ellipticals are proposed to originate from starbursting galaxies in

$z\gtrsim 2$

overdensities. To discern what triggers these starbursts, and their

$z=0$

descendants, we performed a detailed case study of five gas-rich galaxies in the

$z=2.41$

overdensity, HATLAS J084933.4 + 021443. Using

$0.15\,\mathrm{ arcsec}$

resolution CO(4-3), [C I]1-0, and dust-continuum observations, we characterized their cold gas morphology and kinematics. We find two rotating discs, W and C, both of which exhibit non-axisymmetric gas motions. Of the two extreme starbursts, W is a lopsided, rotation-dominated disc with a rotation velocity of

$\sim 520$

km s

$^{-1}$

, whereas T is most likely a merger. Combined with recent studies, we find that

$\gtrsim 44~{{\ \rm per\ cent}}$

of massive, gas-rich starbursts in overdensities are rotation-dominated discs, a fraction not yet systematically reproduced by galaxy evolution models. Beyond

$z=1$

, disc galaxies with rotation velocities of

$\gt 400$

km s

$^{-1}$

frequently appear in overdensities, consistent with early mass assembly in dense environments. By comparing to local early-type galaxies with cold gas discs, we confirm that these systems already reside in haloes comparable to the most massive

$z\sim 0$

ellipticals at the centres of groups and clusters. Despite their extreme star formation rates (SFRs), these discs lie on the same

$\sigma$

--SFR locus as lower SFR field galaxies, implying that stellar feedback remains the dominant turbulence driver. We postulate that this is because inflowing gas is effectively transported through ordered internal streaming, such that only a small fraction of kinetic energy feeds disc-wide turbulence.

Direct Retrieval of Protoplanetary Disk Dust Properties Using Auto-differentiable Gaussian Processes and Their Application to the HD 169142 Disk

First Author: Yoshida, Tomohiro C.
Instruments: ALMA_Band_3, ALMA_Band_6, ALMA_Band_9
ProgramIDs: 2024.1.01254.S, 2013.1.00592.S, 2015.1.01301.S, 2015.1.00490.S, 2016.1.00344.S, 2017.1.00727.S, 2018.1.01716.S
BibCode: 2026ApJ..1007..198Y

Retrieving dust properties in protoplanetary disks, including the surface density distribution, temperature, and grain size distribution, is a fundamental task in observational studies of planet formation. While multiwavelength analysis of the spectral energy distribution (SED) using interferometers such as the Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful diagnostic tool, traditional methods are often hindered by strong biases arising from a limited imaging beam size. In this paper, we present a new retrieval framework for dust disk properties designed to overcome this challenge. We assume that the underlying physical structures are expressed as sample paths from Gaussian processes, compute the radial intensity distributions at observed wavelengths, and produce one-dimensional visibility models. The models are compared with the observed data and the posterior distributions are sampled via the Markov Chain Monte Carlo method. The whole procedure is implemented in JAX, which enables end-to-end auto-differentiation and significantly accelerates the inference. We validate our methodology using mock datasets, and find that the results are not strongly biased and better reproduce the input profiles. We also demonstrate its capabilities through an application to ALMA Band 3, 6, and 9 observations of the HD 169142 disk, revealing a new complex structure. Our developed code is publicly available as a Python module, Flexible Radial Analysis of Protoplanetary Disks. This framework provides a next-generation infrastructure for disk SED modeling, enabling high-precision studies of the physical environments in which planets form.✎ 📗

Spirals and vertical motions in the planet-forming disk around HD 100546: A multiline study of its gas kinematics

First Author: Wölfer, Lisa
Instruments: ALMA_Band_10, ALMA_Band_6, ALMA_Band_7
ProgramIDs: 2011.0.00863.S, 2015.1.00806.S, 2016.1.00344.S, 2018.1.00141.S
BibCode: 2026A&A...712A.177W

Context. The disk around the Herbig star HD 100546 represents a particularly interesting target for the study of dynamical planet--disk interactions, as various features observed in both the dust and gas provide direct and indirect evidence for ongoing planet formation. Aims. In this work, we aim to characterize the gas kinematics of five molecular CO emission lines (¹² CO 7--6, ¹²CO 3--2, ¹²CO 2--1, ¹³CO 2--1, C¹⁸O 2--1), observed with ALMA in HD 100546, to reveal deviations from Keplerian rotation, along with substructures in the peak intensity and line width. Methods. For our analysis, we fit the molecular intensity channels with the DISCMINER package to model the line profiles and extract observables such as the centroid velocity, peak intensity, and line width. In addition to fitting the full cube, we also conducted runs where the blue- and redshifted sides were modeled separately to search for possible asymmetries. Results. Our analysis reveals prominent kinematical spiral features in all five lines on large scales of the disk and we were able to reproduce their morphology with both a linear and logarithmic spiral. In ¹²CO 2--1, spirals are also seen in the peak intensity residuals, while the line width residuals exhibit a prominent ring of enhanced line widths around 125--330 au. The models further show that the emission from the redshifted side may originate from higher disk layers than that from the blueshifted side, with the asymmetry being especially pronounced for ¹²CO 7--6. Conclusions. The pitch angles of the spirals are consistent with those driven by an embedded companion inside of 50 au, suggesting a dynamical mechanism rather than gravitational instabilities. Furthermore, we found indications of a companion around 90--150 au, where tentative dips are present in the radial profiles of the integrated intensity of ¹³CO and C¹⁸O 2--1 and pressure minima are observed in the azimuthal velocities. For the first time, we also detected downward vertical flows in this region, which coincide with the observed dust gap. The asymmetry in the emission heights could be a result of infall from the disk's environment. Another explanation could be the presence of a warped inner disk casting a shadow onto one side of the disk.

Supersolar Metallicity and Tentative Evidence for Photochemistry on WASP-96 b from JWST and Ground-based VLT Transmission Spectroscopy

First Author: Radica, Michael
Instruments: FORS2
ProgramIDs: 199.C-0467
BibCode: 2026AJ....171..314R

With its expanded wavelength coverage and increased precision compared to previous space-based observatories, JWST provides the opportunity to revisit benchmark planets and view them in a new light. Here, we conduct an in-depth study of the atmosphere of the hot-Saturn WASP-96 b combining a new JWST NIRSpec/G395H transit with archival NIRISS/SOSS and Very Large Telescope/FORS2 transmission spectra. The combined spectrum shows clearly visible features from H₂O, CO₂, and Na. CO, though, remains unconstrained, precluding a firm metallicity derivation from free retrievals alone. However, self-consistent grids yield a broadly superstellar atmospheric metallicity of 2─6× stellar. When combined with a roughly stellar C/O ratio ( 0.41−0.09+0.10 from self-consistent grids), we find that WASP-96 b potentially formed via core-accretion beyond the H₂O snowline and subsequently accreted volatile-rich material. Free retrievals also find a moderate preference ( lnB = 2.69) for models with SO₂ versus without. WASP-96 b falls directly on the proposed "SO₂ shoreline" and the retrieved SO₂ abundance is well-matched to predictions from photochemical models. Our combined spectrum displays an optical slope, which our models fit with opacity from scattering aerosols—either small-particle condensate clouds or photochemical hazes—though we cannot completely rule out the broad wings of Na or the effects of stellar contamination. Future observations are necessary to disentangle these effects. Finally, we explore the possibility for limb asymmetry in WASP-96 b's transmission spectrum and provide several tests to identify asymmetries in our data. We encourage the community to prioritize the development of a robust pathway to quantify the presence of limb asymmetry—particularly for low signal-to-noise cases.

The asymmetric structure of the inner disc around HD 142527 A with VLTI/MATISSE

First Author: Scheuck, M. B.
Instruments: GRAVITY, MATISSE, PIONIER
ProgramIDs: 108.225V, 111.254P, 190.C-0963, 106.21Q8, 098.D-0488
BibCode: 2026A&A...708A.380S

Context. Circumstellar discs, and especially their inner regions, which cover ranges from less than 1 au to a few au, are the birthplaces of terrestrial planets. The inner regions are thought to be as diverse in structure as the well-observed outer regions probed by ALMA. Aims. By combining data and results from previous studies using the VLTI/PIONIER and VLTI/GRAVITY instruments with new, multi-epoch VLTI/MATISSE observations, we aim to provide a comprehensive picture of the structure of the inner regions of the circumstellar disc around the F-type Herbig Ae/Be star HD 142527 A, the primary of a binary star system. Methods. We modelled the multi-wavelength interferometric data using a parametrised, geometrically thin disc model, allowing for azimuthal asymmetry, and exploring a first-order disc modulation and an off-centre Gaussian component. Results. We find time-variable structures in the N-band observables, which we reproduce with time-dependent models. This variability manifests as azimuthally asymmetric emission, evidenced by strong, non-zero closure phases in the N-band data. Fits to individual epochs of the N-band observations yield better χ²_r values than fits to all epochs simultaneously. This suggests substantial changes in the geometry of the inner disc emission from ∼1 au up to a few astronomical-unit scales from one year to the next. Moreover, our models produce a very close-in inner disc rim R_rim ≍ 0.1 au. Altogether, we find a very complex, substantially non-point symmetric and temporally variable disc (r_out ≲ 6 au) around the primary. Conclusions. The very close-in inner rim indicates the presence of material within the typical wall-like sublimation radius, R_{rim,literature} ≍ 0.3 au. The complex, temporally variable inner-disc geometry is likely affected, or even caused by, the close passage (∼5 au) and short orbit (P ≍ 24 yr) of the companion HD 142527 B.

A New Cloud─Cloud Collision Source N68 toward the G35 Molecular Cloud Complex

First Author: Chen, En
Instruments: LABOCA
ProgramIDs: 085.F-9526, 085.F-9505, 082.F-9701, 080.F-9701, 081.C-9501, 079.C-9501, 078.F-9040, 181.C-0885
BibCode: 2026ApJ..1001..230C

Bubble N68 in the G35 complex shows clear cloud─cloud collision (CCC) signatures. Its semiring-like morphology harbors many significant massive star formation tracers: 6 H II regions, 4 6.7 GHz masers, 5 Midcourse Space Experiment sources, 9 radio peaks, and nearly 10 O/B-type stars. We also identified 163 young stellar objects (45 Class I, 5 Flat, 113 Class II), indicating active star formation toward N68. Our molecular study with CO reveals two distinct molecular clouds (N68a: 47─56 km s⁻¹; N68b: 56─64 km s⁻¹), with broad bridge features and complementary distributions at their borders, indicating an ongoing CCC. Star formation in N68 is collectively driven by collect-and-collapse (CC), radiation-driven implosion, and CCC mechanisms. However, compared with the CC and radiation-driven implosion mechanisms, the CCC mechanism does not enhance the star formation efficiency; instead, it tends to trigger the formation of massive stars. N68, along with bubbles N65 and N61, constructs a ∼100 pc scale CCC system in the G35 complex.

Toward Early-type Eclipsing Binaries as Extragalactic Milestones: First Calibration of the SBCR from O- and B-type Stars in Detached Eclipsing Binaries

First Author: Taormina, Mónica
Instruments: SOFI, VIRCAM
ProgramIDs: 179.B-2003, 0102.D-0469, 0102.D-0590
BibCode: 2026ApJ..1002L..20T

To measure precise distances beyond the Magellanic Clouds and determine an accurate value of the Hubble constant, eclipsing binary systems composed of early-type stars can play a crucial role. However, it is fundamental to first obtain a reliable empirical surface brightness─color relation (SBCR) for the hottest possible stars. Based on our previous study of six detached eclipsing binaries composed of O- and B-type stars in the Large Magellanic Cloud, we calibrated the SBCR using 12 stars with V − K_s < ─0.6 mag. We found a significant difference between O-type and B-type stars in SBCRs, which are clearly separated in mass. The relation based on B-type stars is consistent with the relation for redder stars from the literature. This allowed us to provide a combined relation valid for stars less massive than ∼16 M_⊙in the wide color range −0.9 < V − K_s < 2.1 mag, with σ = 0.025 mag. Such a relation can provide extragalactic distances precise to as high as ∼1.2% given the sufficient quality and number of target objects. The relation for O-type stars (σ = 0.055 mag) remains uncertain due to its strong dependence on the method used to determine reddening and requires further study. However, we tested it on the only known eclipsing system in M33 and obtained distance modulus DM = 24.90 ± 0.17 mag, which perfectly agrees with the published distance to the system.

Large-scale environments of star-forming active galactic nuclei: How black-hole mass, accretion rate, and luminosity connect to dark-matter halos

First Author: Mountrichas, G.
Instruments: VIMOS
ProgramIDs: 182.A-0886
BibCode: 2026A&A...708A.323M

Understanding the relative roles of large-scale environment and internal host-galaxy processes in shaping active galactic nuclei (AGN) activity is key to constraining models of black-hole growth and galaxy evolution. In this work, we investigated how the environment of X-ray-selected active galactic nuclei (AGNs) relates to black-hole growth and accretion properties, and whether these introduce a dependence on a large-scale environment beyond that set by the host galaxy itself. By combining the XXL and Stripe 82X surveys, we assembled samples of 427 broad-line AGNs at 0.5 < z < 1.2 and over 20 000 galaxies, with host-galaxy properties consistently derived using the same spectral energy distribution fitting methodology and assumptions. Dark-matter halo (DMH) masses were inferred from AGN─galaxy cross-correlation functions, while a multivariate nearest-neighbour matching algorithm was applied to isolate trends with black-hole mass (M_BH), Eddington ratio (λ_Edd), and X-ray luminosity (L_X) under controlled host-galaxy conditions. Within the statistical uncertainties of the present dataset, we find that X-ray AGNs typically reside in halos of log(M_DMH/h⁻¹ M_⊙)≃13, with no significant variation as a function of M_BH, λ_Edd, or L_X. Neither M_BH nor λ_Edd shows a measurable correlation with large-scale environment, which is consistent with a scenario in which long-term black-hole growth and short-term accretion variability are primarily regulated by internal host-galaxy processes rather than halo-scale mass alone. The absence of a statistically significant M_DMH─L_X trend further indicates that AGN radiative output reflects stochastic or feedback-regulated variability, rather than direct modulation by the large-scale environment. Overall, these results support a self-regulated co-evolution framework in which large-scale structure sets the boundary conditions for gas availability and AGN duty cycle, while the subsequent growth and luminosity evolution of AGNs are determined predominantly by local processes within their host galaxies.

A search for optical counterparts in quiescent black hole X-ray transients

First Author: Yanes-Rizo, I. V.
Instruments: FORS2, ULTRACAM_NTT
ProgramIDs: 69.D-0644, 110.24A3, 106.213W
BibCode: 2026A&A...708A.298Y

Dynamical mass measurements of compact stars in X-ray transients demand the detection of optical/near-infrared counterparts in quiescence. Out of the 73 black hole candidates in X-ray transients, optical and near-infrared quiescent counterparts have only been identified for 34 objects. We present ULTRACAM photometric observations of nine candidate black hole X-ray transients with no reported counterparts in quiescence, complemented with data from the public surveys, DECaPS and Pan-STARRS. In addition, we analyze photometry of three sources (SWIFT J1539.2-6227, XTE J1817-330, and XTE J1818-245) obtained during their discovery outburst. The data provide the first optical identifications and precise astrometry of four targets (MAXI J1348-630, SWIFT J1539.2-6227, XTE J1726-476, and XTE J1817-330) plus 3σ lower limits to the quiescent optical magnitudes for an additional five (MAXI J0637-430, 4U 1755-338, MAXI J1803-298, XTE J1818-245, and MAXI J1828-249). Of these five, 4U 1755-338 was found to be active during our ULTRACAM observations, and we used our images to derive refined astrometric coordinates. We used the photometric magnitudes and colors to place preliminary constraints on the orbital periods and spectral types of the companion stars. Finding charts of all the targets are also provided to facilitate future follow-up studies. Finally, we present updated astrometry for XTE J1650-500 using archival FORS2 images.

Constraining small planet compositions for future missions

First Author: Palethorpe, Larissa
Instruments: ESPRESSO, HARPS
ProgramIDs: 0103.C-0289, 098.C-0860
BibCode: 2026MNRAS.548ag520P

Accurate mass and radius measurements of small transiting exoplanets are essential for probing their compositions, formation histories, and potential habitability. We present a uniform analysis of six planetary systems (each hosting at least one small transiting planet): K2-79, K2-106, K2-111, K2-222, K2-263, and TOI-1634. Our study combines new CHEOPS transit observations with archival photometry from K2, TESS, and ground-based facilities, alongside new and archival radial velocity data from HARPS-N, HIRES, ESPRESSO, and others. For each system, we perform joint transit and RV modelling, achieving typical precisions better than 15 per cent and 5 per cent for mass and radius, respectively, and thus enabling precise bulk density determinations. These reveal a range of compositions, including rocky planets near the radius valley (e.g. K2-106 b, TOI-1634 b), intermediate-density planets requiring steam-rich or mixed volatile envelopes (e.g. K2-111 b, K2-263 b), and low-density regimes, consistent with gas dwarfs or water-worlds (e.g. K2-79 b, K2-222 b). Several systems show evidence of additional companions detectable via RVs but not seen in transit. The results highlight the value of coordinated CHEOPS and HARPS-N observations in delivering some of the most precise bulk densities for small planets to date and support the preparation for future atmospheric characterization missions.

Evolution of the early-type fraction in massive galaxies at z < 2: how did early-type morphology form?

First Author: Kajisawa, Masaru
Instruments: VIMOS
ProgramIDs: 1100.A-0949, 194.A-2005, 185.A-0791, 175.A-0839
BibCode: 2026MNRAS.548ag551K

Using James Webb Space Telescope/NIRCam data over a 0.28 deg

$^{2}$

area from COSMOS-Web survey, together with Hubble Space Telescope/Advanced Camera for Surveys data, we investigate early-type fraction of massive galaxies with

$M_{\rm star}\gt 10^{10.5}\,\mathrm{ M}_{\odot }$

$0.2\lt z\lt 2.0$

, and explore the formation of their early-type morphology. We measure concentration index C (

$=R_{80}/R_{20}$

) and asymmetry index A, and select early-type galaxies with

$C\gt C_{n=2.5}$

and

$A_{\rm cor}\lt 0.2$

. Here,

$C_{n=2.5}$

is the concentration expected for a Sérsic profile with

$n=2.5$

under the spatial resolution and depth of the data, and

$A_{\rm cor}$

is the asymmetry corrected for resolution effects. The fraction of early-type galaxies with

$M_{\rm star}\gt 10^{11}\, \mathrm{M}_{\odot }$

(

$=10^{10.5}$

─

$10^{11}\, \mathrm{M}_{\odot }$

) decreases with increasing redshift from

$\sim$

70 per cent (

$\sim$

40─60 per cent) at

$z\sim 0.3$

$\sim $

20─25 per cent (

$\sim$

15─25 per cent) at

$z\sim 1.8$

. We also examine the evolution of their

$R_{20}$

and

$R_{80}$

, which enclose 20 per cent and 80 per cent of the total flux of the galaxy, respectively. The median

$R_{80}$

shows strong mass dependence and significant redshift evolution, whereas the median

$R_{20}$

shows little dependence on either stellar mass or redshift. In contrast, morphological differences are more pronounced in

$R_{20}$

than in

$R_{80}$

: the median

$R_{20}$

of early-type galaxies is smaller than that of late-type and irregular galaxies by 0.25─0.45 and 0.3─0.6 dex, respectively. The median SSFR (specific star formation rate) of sample galaxies strongly correlates with

$R_{20}$

, and early-type galaxies have lower SSFRs by

$\sim 1$

dex. We further find that early-type galaxies at

$z\gtrsim 1.3$

have younger mass-weighted stellar ages of

$t_{\rm mw}\lesssim 2$

Gyr than late-type and irregular ones. Their SSFRs,

$t_{\rm mw}$

, and morphological properties suggest that these high-z early-type galaxies experienced rapid formation of a dense stellar core through starburst, followed by quenching of star formation, and subsequently resumed star formation

$\sim$

1─2 Gyr later.

AGN in massive galaxies identified via optical broad-band variability: lessons from VST-COSMOS for future LSST science

First Author: Bichang'a, B.
Instruments: OMEGACAM
ProgramIDs: 088.D-4013
BibCode: 2026MNRAS.547ag287B

We study the properties of 56 massive (M

$_{\rm {\star }}$

> 10

$^{10}$

$_{\odot }$

) galaxies at

$z\lt 1$

that host AGN, detected via their broad-band optical variability in the VST-COSMOS survey. VST-COSMOS provides a nearly identical single visit depth (r

$\sim$

24.6 mag) and temporal baseline (eleven years) as the forthcoming Legacy Survey of Space and Time (LSST), albeit in a much smaller 1 deg

$^2$

footprint (four orders of magnitude smaller than that of the LSST). We compare the properties (morphologies, the presence of interactions, rest-frame colours and environment) of our AGN to galaxies in a control sample, which are drawn from the non-variable population and matched in redshift and stellar mass to their AGN counterparts. The fraction of AGN with early-type morphology (

$\sim$

55 per cent) and the fraction that is interacting (

$\sim$

23 per cent) are similar to what is observed in the controls, suggesting that these AGN are not primarily triggered by interactions. Similarly, the AGN and controls do not show strong differences in their rest-frame

$(u\!-\!z)$

colours or local environment, suggesting that neither the recent star formation histories nor the surroundings of the AGN are strongly atypical of the general galaxy population. This study provides a glimpse into forthcoming AGN science using the LSST. With vastly improved statistics, LSST will offer unprecedented insights into AGN demographics, host-galaxy evolution and the processes that fuel supermassive black holes, potentially reshaping our understanding of their place in the Universe.

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