Abstracts

Mid-infrared JWST spectra of carbon stars in the Large Magellanic Cloud

G. C. Sloan, B. Aringer, Kathleen E. Kraemer, J. Cami, K. Eriksson, S. Hoefner, K. Justtanont, E. Lagadec, Paola Marigo, M. Matsuura, I. McDonald, E. J. Montiel, R. Sahai and A. A. Zijlstra

Mid-infrared spectra from the Medium Resolution Spectrometer on the James Webb Space Telescope have revealed the molecular chemistry of carbon stars in the Large Magellanic Cloud with better resolution and sensitivity than previously possible. Our sample spans a range of dust-production rates and includes three relatively dust-free semiregular variables and six dustier Mira variables. All were observed 15-20 yr earlier with the Infrared Spectrograph on the Spitzer Space Telescope at lower spectral resolution. The new spectra show that the C3 molecule is responsible for a strong absorption band centered at 5.2 um. CS is clearly present in some of the sample, especially the stars with less dust. HCN also appears to be present. Some of the spectra have changed significantly between the Spitzer epoch and the MRS observations in 2023 and 2024, and in most cases these changes can be attributed to the stellar pulsation cycle. One exception is the disappearance of a dust emission feature at 18 um in one of the Miras. The new spectra reveal a dip centered at 10 um, which could arise either from an unknown carrier or from variable molecular emission to the red and blue. The presence of this spectral structure on the short-wavelength side of the SiC dust emission feature at 11.3 um along with the broad C2H2 band centered at 14 um raise the possibility that some previously reported detections of weak SiC dust emission in other carbon stars may not be real.

Reference : 2026, ApJ, 1002, 115
URL : https://iopscience.iop.org/article/10.3847/1538-4357/ae5a24

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

B. Pimpanuwat, S. Etoka, M. D. Gray, A. M. S. Richards, A. Baudry, F. Herpin, T. Danilovich, L. Decin, M. O. Lewis, I. El Mellah, C. A. Gottlieb, Y. Mori, H. S. P. Müller, R. Sahai, K. T. Wong, J. A. Yates, and A. Zijlstra

Silicon monoxide (SiO) traces the physical conditions and dynamics in the circumstellar envelopes (CSEs) of AGB stars. We present high-resolution ALMA Band 6 observations of highly excited SiO emission in 14 oxygen-rich AGB stars. We cover transitions from v = 0 to v = 8, including first detections of 28SiO v = 3, 4, 8, J = 6-5, 29SiO v = 6, J = 6-5, and 30SiO v = 4, 5, J = 6-5, some of which are masers. The v = 8 transition is the highest v-state observed in an AGB star yet. Masers in v = 0 are detected clearly in V PsA and IRC+10011 and tentatively in T Mic. R Hya exhibits the richest SiO spectrum. SiO J = 6-5 absorption is seen in R Aql, R Hya, S Pav, and T Mic, with features indicative of both infalls and outflows, and tentative detection of 28SiO v = 8, J = 6-5 absorption is found towards S Pav and R Aql. Highly excited SiO emission is often distributed in arcs or clumps with velocity gradients; components in R Hya and U Her align with predicted shock fronts. Detection rates show no significant difference between low and high mass-loss rate stars, although line overlap may affect some intensities. Maser detections appear uncorrelated with pulsation period or phase. The radius enclosing 90 per cent of compact SiO emission shows a tentative correlation with mass-loss rate. These results highlight the role of mass loss and CSE geometry in shaping high-excitation SiO emission.

Reference : accepted in MNRAS
URL : https://arxiv.org/abs/2605.05760

VLTI/PIONIER imaging of post-AGB binaries. An INSPIRING hunt for inner rim substructures in circumbinary discs

T. De Prins, A. Corporaal, J. Kluska, D. Kamath, H. Van Winckel, K. Andrych, J. Alcolea, N. Anugu, J.-P. Berger, V. Bujarrabal, I. Gallardo Cava, S. Kraus, H. Olofsson

Post-asymptotic giant branch (post-AGB) binaries are surrounded by stable dusty discs. Despite extensive evidence for
disc-binary interactions and complex morphologies, systematic studies of the inner disc rim morphology and dynamics are lacking. We image the detailed inner rim morphology for a sample of ’full’ post-AGB circumbinary discs observed using NIR interferometry. At resolutions down to 1−2 mas (corresponding to 1−10 AU), we aim to reveal potential substructures that may trace perturbations from the binary or embedded substellar companions, or that arise from hydrodynamical instabilities. We developed a systematic image reconstruction workflow using the SPARCO approach together with the ORGANIC
reconstruction algorithm. This was applied to VLTI/PIONIER data of eight diverse post-AGB binaries obtained within the INSPIRING
ESO large programme, providing high-fidelity images of dust continuum emission at the inner rim. Extensive tests were applied to assess the robustness of the recovered image features. The dusty disc rim is well-resolved for all targets. Only one of the images can be fully accounted for by simple radiative
transfer effects due to disc inclination, while in several others indications of potential substructures are detected. Strikingly, four exhibit robust azimuthal brightness enhancements at locations not expected from inclination effects alone. These can indicate strong radiative or dynamical responses to the binary, or vortices formed via hydrodynamical instabilities. One target — IW Car — displays an even more puzzling morphology, showing a single large-scale outer flux arc and several small-scale arcs closer to the binary, possibly revealing accretion streams onto the binary, a misaligned innermost disc, or a spiral feature located in the disc or in an outflow. This work presents the first homogeneous interferometric imaging survey of the inner regions of post-AGB circumbinary discs, enabling direct comparison of inner rim morphologies across a representative sample. The inner disc regions are highly diverse and dynamic, harbouring a significant amount of substructure candidates. Multi-wavelength and time-series imaging will be essential in constraining the extent, motion and wavelength-dependence of these features, and uncover their physical origins.

Reference : De Prins, T, et al. 2026, A&A; accepted for publication
URL : https://arxiv.org/abs/2605.13445

Charting circumstellar chemistry of carbon-rich asymptotic giant branch stars III. SiO and SiS abundances

Unnikrishnan R., De Beck E., Nyman L.-Å., Olofsson H., Vlemmings W. H. T., Maercker M., Van de Sande M., Millar T. J., Danilovich T., Andriantsaralaza M., Charnley S. B., Rawlings M. G.

The circumstellar envelopes of AGB stars are sites of rich molecular chemistry. The present understanding of C-rich AGB chemistry largely relies on observations of the archetypal carbon star IRC+10 216. Current molecular abundance estimates for carbon stars are based either on single-dish spectra sampling a range of excitation conditions, or on interferometric mapping of a few lines.
We aim to estimate the circumstellar abundances of SiO, SiS, and their most abundant isotopologues ( ²⁹ SiO, ³⁰ SiO, ²⁹ SiS, ³⁰ SiS, and Si ³⁴ S) for a sample of five carbon stars. This study compares molecular abundances across the sources, tests chemical modelling predictions, and examines whether IRC+10 216 is representative of the broader carbon star population.
We derived molecular abundances using detailed 1D non-local thermodynamic equilibrium (non-LTE) radiative transfer (RT) modelling, constrained by both morphological and excitation information obtained from spatially resolved ALMA maps and single-dish observations. We further compared the derived abundances to chemical modelling results.
We obtain good fits to the SiO and SiS line profiles, and derived well-constrained abundance profiles and reliable isotopic ratios for all sources except AFGL 3068. While the SiS peak abundances are very similar across the sample (2.0 × 10 ⁻⁶ –4.7 × 10 ⁻⁶ ), we find that the SiO peak abundances of the rest of the stars are a factor of 5 larger than that of IRC +10 216. The e -folding radii ( R _e ) are in the range 1.3 × 10 ¹⁶ − 7.0×10 ¹⁶ cm for SiO and 6.0 × 10 ¹⁵ − 1.0×10 ¹⁷ cm for SiS. The R _e increases with gas density for both SiO and SiS. Our RT models cannot simultaneously fit the low- and high- J SiO lines of IRC+10216. Chemical models reproduce the derived SiO abundance profiles well, while over-predicting the SiS R _e values.
Our models highlight the necessity of having spatially resolved observations across a broad range of excitation conditions to robustly constrain molecular abundance profiles, while also making evident the limitations inherent in 1D RT modelling using simplified (circum)stellar models. We find that the currently assumed SiS photodissociation rate in chemical models is underestimated.

Reference : 2026 Astronomy & Astrophysics, 709, A216
URL : https://www.aanda.org/10.1051/0004-6361/202558602

OH/IR stars in the inner Galactic bulge: I. Colour, CO line, and stellar light curve characteristics

Olofsson H., Khouri T., Muller S., Unnikrishnan R., Groenewegen M.A.T., Blommaert J.A.D.L., De Beck E., Kastner J.H., Maercker M., Patel N., Ryde N., Sargent B.A., Srinivasan S., Vlemmings W.H.T.

Stars on the asymptotic giant branch (AGB) play important roles in a number of astronomical contexts. To quantify these roles, it is necessary to establish the mass-loss characteristics of stars as they evolve up and beyond the AGB. We used an equidistant sample of 77 AGB stars in the inner Galactic bulge, selected on the existence and strength of OH1612 MHz maser emission, to obtain information on the mass loss of O-rich AGB stars, and on its transformations in geometry and kinematics that occur at the tip of the AGB. Observations of circumstellar lines from several rotational transitions of 12CO, 13CO, and C18O were performed with the Atacama Large Millimeter/submillimeter Array (ALMA), and, for a sub-sample, with the Atacama Pathfinder EXperiment telescope (APEX). The ALMA observations also provide continuum data. Existing infrared photometry was used to estimate colours and produce stellar light curves. Based on mid-infrared colour, CO line, and near-infrared variability characteristics, the objects were divided into four categories of distinct stellar and/or circumstellar properties. Various circumstellar CO line characteristics are presented and compared between the categories, such as morphologies and extents of brightness distributions (BDs), line profiles (LPs), line intensity ratios, and kinematics. A majority of the objects form a homogenous group with sharply, centrally peaked BDs and LPs of the soft-parabola type, while the rest show extended and complex BDs and/or LPs with high-velocity wings. The C18O line and ALMA continuum detection rates vary significantly between the categories. CO line emission is also detected from interaction zones where the expanding circumstellar gas meets the interstellar medium. These data provide the foundation for more detailed studies, including radiative transfer analyses of the CO line and photometry data, on the evolution of stellar and circumstellar characteristics of O-rich stars on the upper AGB and beyond.

Reference : 2026 Astronomy & Astrophysics, accepted
URL : arXiv:2605.26605

Ancient ‘ghost’ planetary nebulae discovered with amateur telescopes

Manuel J. A., Jones D., Santander-García M., Reindl N.

As planetary nebulae evolve, they fade and dissipate into the surrounding interstellar medium, which makes them harder to detect. Modern, advanced amateur equipment can help to uncover this hidden population of ancient ‘ghost’ planetary nebulae. Via careful processing of long-integration, narrow-band imagery with modest aperture telescopes at a dark-sky site, we detected three new candidate planetary nebulae (JAM 2, JAM 3, and JAM 4). Each measures several arcminutes across with [O III] surface brightnesses of order 30 mag / arcsec². For each nebula, we identify a candidate central star, the parallaxes of which lead to nebular age estimates in the range 50–100 thousand years. The candidate central star of JAM 2 also shows indications of photometric variability, potentially due to spots on the stellar surface.

Reference : 2026 Astronomy & Astrophysics, 710, A68
URL : https://www.aanda.org/10.1051/0004-6361/202659488

Annoucements

Open invitation to join the ALMA2040 Sun+Stars Science Working Group

Following ESO’s Expanding Horizons initiative, the mm/submm community began organising within Europe and is now expanding to a global effort to define a next-generation interferometric facility for the 2040s (“ALMA2040”) (https://www.euroalma2040.com). Researchers worldwide are invited to contribute to scientific and technical White Papers and help shape a coherent, globally coordinated concept for a next-generation sub-mm interferometric facility operational in the 2040s.
Here we ask all of you who are interested in mm/submm evolved star science to consider joining the ALMA2040 Sun+Stars Science Working Group or other working groups that you are interested in (see https://www.euroalma2040.com/working-groups).
There are various ways to join. The easiest is to contact the SWG leads (see below) directly and ask to be added to the mailing list. You can also fill out the form here (https://www.euroalma2040.com/contact_1). If you fill out the form, you should be directed to the mailing list that you can subscribe to (note that there is a general list as well as the individual SWG lists), although invitations are known to end up in spam folders.

The next step in the ALMA2040 process is producing ALMA2040 white papers (abstracts of several that are being prepared can be found here: https://www.euroalma2040.com/white-papers). These are coordinated via the SWGs. The Sun+Stars is currently preparing three white papers (current coordinators in brackets):
– Evolved Stars, multiplicity and planets: Shaping and Being Shaped by Stellar Evolution [Theo Khouri, Elvire De Beck, Tomek Kaminski]
– Evolved Stars: Dust formation/mass loss [Luis Velilla-Prieto, Guillermo Quintana-Lacaci, Wouter Vlemmings]
– The energetic atmosphere of the Sun: How do small-scale dynamic processes heat and structure the solar atmosphere? [Sven Wedemeyer, Miroslav Barta, Astrid M. Veronig, Stanislav Gunár]

If you have an idea that does not fit these papers, and you want to coordinate a white paper on it, please contact the SWG leads with your suggestion. But you are all also very welcome to join if you mainly want to support the effort and want to remain informed.

Looking forward to hearing from many of you.
Wouter Vlemmings (wouter.vlemmings.at.chalmers.se)
Theo Khouri (theo.khouri.at.chalmers.se)
Sven Wedemeyer (sven.wedemeyer.at.astro.uio.no)