Abstracts

TESS Asteroseismology of Red Giants in the Old Super-Solar Metallicity Open Clusters NGC 188 & NGC 6791

Howell, Madeline, Johnson, Jennifer A., Pinsonneault, Marc H., Morales, Leslie M., Tayar, Jamie, Roberts, John D., Stello, Dennis, McKenzie, Madeleine

Open clusters are fundamental laboratories for investigating stellar and Galactic evolution, and serve as important benchmarks for asteroseismic analyses. Using a boutique method to analyze TESS photometry, we study red giants in two old super-solar metallicity open clusters: NGC 188 & NGC 6791. By comparing Kepler and TESS observations for NGC 6791, similar oscillation mode frequencies are recovered, however we find a systematic offset of 2.2% with a scatter of 9% in the $ν_\textmax $ measurements. We attribute this discrepancy to the lower signal-to-noise of the TESS data for these relatively faint stars. For the brighter cluster NGC 188, we present new seismic measurements in 17 red giants. We estimate average seismic masses for the RGB of $M_\textRGB,NGC188 = 1.13\pm0.04$(rand)$^+0.12_-0.19$(sys) $M_\odot$ and RC of $M_\textRC,NGC188 = 1.11\pm0.01$(rand)$^+0.11_-0.19$(sys) $M_\odot$, consistent with independent mass estimates for this cluster and with similar precision to previous Kepler studies. From the difference between the average evolutionary phase masses, we estimate an integrated RGB mass loss of $ΔM = 0.02 \pm 0.04$(rand)$\pm0.01$(sys) $M_\odot$, supporting the evidence for lower mass loss at higher metallicities. Using asteroseismology and chemical abundances, we identify three binary interaction candidates: two under-massive stars and one over-massive star potentially exhibiting dipole-mode suppression. Finally, we derive an average seismic cluster age of $7.0\pm0.9$ Gyrs, in good agreement with previous literature ages. Our analysis demonstrates the strong potential of TESS asteroseismology for open clusters, and motivates extending this investigation to other TESS clusters that span a wider range of ages and metallicities.

Reference : 2026 27 Pages, 12 Figures, Accepted to ApJ
URL : https://arxiv.org/abs/2604.27828

Dust Formation in Common Envelope Binary Interactions — III. Lightcurves

Mu, Chunliang, De Marco, Orsola, Bermúdez-Bustamante, Luis C., Hirai, Ryosuke, Price, Daniel J., Siess, Lionel, González-Bolívar, Miguel, Lau, Mike Y. M., Blagorodnova, Nadejda

Luminous red novae are transient events thought to arise from common envelope binary interactions. In this paper, we perform post-processing light-curve calculations for two, 3D hydrodynamic simulations of common envelope events. These simulations model interactions between 1.7 $M_\odot$ and 3.7 $M_\odot$ asymptotic giant branch stars and a 0.6 $M_\odot$ compact companion, including dust nucleation. In both our simulations, which are carried out for 44 years under adiabatic conditions, we observe a bright, hot peak lasting $3-5$ years, primarily due to the expansion of the photosphere before and during inspiral. Additional peaks can be seen appearing at different times and for different viewing angles, due to the asymmetry of the interaction. Dust forms about $1-3$ years after the beginning of the simulated interaction and shortly afterwards we witness a sharp decline in the bolometric luminosity, followed by a partial recovery and a plateau with an effective temperature of $\sim$400 K. The dust photosphere reaches a size of $\sim$250 au by the end of the simulations, but we predict that between 100 and 200 years, the dust will become optically thin at visible wavelengths, revealing an inner, warmer photosphere. The lightcurves obtained have two, well-quantified, but large uncertainties: insufficient surface resolution primarily affecting the first 1-2 years of the simulated lightcurves and the adiabatic assumption that affects primarily the later years. We finally contextualise our simulations within a group of observed luminous red nova transients, drawing particular attention to the outburst of OGLE-2002-BLG-360 and AT 2025abao, which are the closest match to our simulation.

Reference : 2026 23 pages, 18 figures, submitted to MNRAS
URL : https://arxiv.org/abs/2606.26495

Analysis of far-infrared fine-structure emissions from the red supergiant μ Cephei

Wiesemeyer H., Marinho L., Harper G.M., Baudry A., Herpin F., Ricken O.

The complex structure and dynamics of red supergiant stars (RSGs) and their variability hinder the spectral analysis of the conditions above their photosphere. RSGs share these features with their lower-mass equivalents on the asymptotic giant branch, but they are less well understood. Since RSGs are the direct progenitors of core collapse (Type II) supernovae, a better characterization is desirable.
This work aims to create a concordant model unifying stellar parameters, elemental abundances, and chromospheric properties of μ Cephei, which is among the most luminous RSGs of the Galaxy. Its distance is weakly constrained (reported values range between 390 and 870 pc), and the immediate vicinity of the photosphere is still largely uncharted territory.
For this purpose, we conducted high-resolution spectroscopy of the transparent far-infrared fine-structure line emissions from the electronic ground states of O I, C II, S I, and Fe II, with the EXES and GREAT instruments flown aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Line-area ratios were compared with predictions from a grid of model chromospheres around an early-M-type RSG. We used a distance of 421 (+57, -42) pc, obtained by linking spectroscopic estimators for μ Cephei to its near-infrared interferometry, which are both available in the literature. The uptake of the observed species by the thermal-equilibrium chemistry in the inner circumstellar envelope was modeled including 523 gaseous and 190 solid species. We applied a dedicated code for the mixed radiative transfer of spectral-line and continuum emissions. The underlying opacities were obtained from statistical-equilibrium calculations and a two-component dust model comprised of silicate and alumina. The velocity structure required to match the observed line profiles accounts for bulk motions and turbulence in the stellar wind, and for the onset of a radiation-pressure-driven wind at the dust condensation zone.
We identify two solutions differing in chromospheric temperature and density. The resulting thermal pressures are within a factor of four. For a clumpy medium, these models reproduce the measured line fluxes, but they require an additional source for the CII abundance, which is most likely the photo-chemistry of carbon. It is driven by far-UV emissions from shocks forming in response to, for example, encounters of outflowing and inflowing gas. A self-consistent model calls for more accurate elemental abundances at the stellar surface. For the other species, the corrections are smaller. Our models also reproduce the λ21 cm flux from the recent literature.

Reference : 2026 Astronomy & Astrophysics, forthcoming
URL : https://www.aanda.org/10.1051/0004-6361/202660113

JWST NIRCam and MIRI Reveal the Dust-Producing AGB Population of NGC 6822

Nally, Conor, Jones, Olivia C., Lenkić, Laura, Ferguson, Annette M. N., Habel, Nolan, Hirschauer, Alec S., Meixner, Margaret, Kavanagh, P. J., Boyer, Martha L., Nayak, Omnarayani, Sargent, B., Scicluna, P.

We present a photometric catalogue of the Local Group dwarf galaxy NGC 6822 based on deep JWST observations obtained with the Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). Point-spread-function photometry and band matching were performed with StarbugII. The resulting catalogue contains 864,114 NIRCam point sources and 17,235 MIRI detections, with 10,079 detected in both instruments. Blackbody fitting yields effective temperatures and bolometric luminosities for 119,621 stars, providing a detailed view of the resolved stellar content. Candidate evolved stars were selected from NIRCam-MIRI colour-magnitude diagrams, with the sample refined by removing resolved contaminants and excluding young stellar objects through spectral energy distribution (SED) fitting. The final sample of 1226 evolved stars was analysed using the Grid of Red Supergiant and Asymptotic Giant Branch Models (GRAMS), from which dust-production rates were obtained and carbon-rich or oxygen-rich asymptotic giant branch (AGB) classifications assigned via a likelihood-weighted comparison across the full model set. Across the JWST fields, evolved stars return 5.6 x 10^-7 Msun yr^-1 of dust to the interstellar medium, with oxygen-rich AGB stars contributing 60% and carbon-rich AGB stars 35%, despite the low metallicity of NGC 6822. The unexpectedly high oxygen-rich contribution indicates the presence of intermediate-mass AGB stars undergoing hot-bottom burning, in line with the recent star-formation history of NGC 6822. Dust-producing AGB stars exhibit a centrally concentrated carbon-rich population and a more extended oxygen-rich population. We also identify JWST colour relations that provide robust photometric estimators of dust-production rates for evolved stars.

Reference : 2026 19 pages, 14 figures. Accepted for publication in MNRAS. The accompanying catalogue contains photometry for 864,114 NIRCam sources and 17,235 MIRI sources, including derived effective temperatures and bolometric luminosities for 119,621 stars and dust-production rates for 1226 evolved stars. The catalogue will be available through VizieR upon publication
URL : https://arxiv.org/abs/2607.11682

29SiO and 30SiO J=1—0 maser signatures in Galactic AGB stars: the impact of third dredge up and turbulence velocity

Lewis, M. O., Sjouwerman, L. O., Pihlström, Y. M., van Langevelde, H. J., Bhattacharya, R., Stroh, M. C

J=1—0 SiO masers at 43 GHz have a well-established distinctive signature in asymptotic giant branch (AGB) stars. 28SiO transitions typically dominate these spectra with the v=1 and v=2 emission being especially prominent and ubiquitous. Several predictions about enhanced 29SiO abundances in exotic stars prompt us to catalog the cases where 29SiO maser emission is enhanced compared to 28SiO. Our purpose is to catalog the known cases of 43 GHz spectra dominated by emission from isotopologue transitions (iso-dom spectra), to explore the commonalities in these sources, and to explain the cause of such maser signatures. Our catalog is drawn from SiO maser line ratios in the infrared-color-selected BAaDE survey and supplemented with a literature detection. The BAaDE catalog has cemented the typical signature of 43 GHz SiO masers, showing it is dominated by the v=1 and v=2 lines. Thirty-five iso-dom spectra are identified, meaning that this signature is seen in about 0.2% of our SiO maser-bearing stars. Their infrared colors are blue compared to other sources of the same period, similar to all sources displaying isotopologue masers. It is clear that the iso-dom nature of sources is variable, but unclear whether this is tied to stellar phase. A large abundance abnormality among the iso-dom sources is disfavored as the iso-dom sources do not appear significantly different from other stars which host isotopologue masers. Maser pumping, affecting the population inversions of specific transitions, can instead explain the enhanced signatures. We posit that iso-dom spectra appear in AGB stars which have undergone third-dredge up (enhancing the 29SiO and 30SiO abundance slightly) and which, in addition, are experiencing very low turbulence velocity (<1 km/s), creating a line overlap which pumps the maser transitions very efficiently.

Reference : accepted by A&A
URL : https://arxiv.org/abs/2605.21678

Most of the Dusty AGB Stars in M31 are Oxygen-rich

Steven R. Goldman, Martha L. Boyer, and Ava L. Allen

In S. R. Goldman et al. (G22), ∼350,000 Thermally Pulsing Asymptotic Giant Branch (TP-AGB) stars were identified in the Andromeda Galaxy (M31). While isolating the highest-quality sample and determining chemical types, an opportunity was missed to include chemical classifications for a subset of the dustiest AGB stars. These sources were identified as dusty using Spitzer mid-infrared photometry in G22, but their circumstellar chemical types (oxygen-rich or carbon-rich) were undetermined because they were not included in the pre-existing Hubble (HST) catalog that was used to classify the stars, owing to overly strict magnitude cuts. Relaxing these restrictions increases the number of dusty AGB stars by 28%, and the ratio of dusty carbon stars to dusty oxygen-rich (M-type) stars from 16% to 20%; however, the sample is still dominated by oxygen-rich stars. This work reaffirms that most of the dusty AGB stars in M31 (and other metal-rich galaxies) have oxygen-rich circumstellar chemistry.

Reference : 2026, Res. Notes AAS, 10, 204
URL : https://iopscience.iop.org/article/10.3847/2515-5172/ae8dbd

CO Second Overtone Line Variability in Three Carbon-rich Early Post–Asymptotic Giant Branch Stage Stars

Puķītis Kārlis

Abstract
Near-infrared CO molecular lines are suggested to be linked with dynamic processes in post–asymptotic giant branch (post-AGB) stars; however, they have not been investigated at high spectral resolution. CO second overtone line variability in the H band is presented for the cool carbon-rich post-AGB stars IRAS 22272+5435, IRAS Z02229+6208, and IRAS 20000+3239. CO features are observed to change intensity, shape, and radial velocity as well as switch between emission and absorption during the pulsation cycle. At all times, the CO line positions are located no more than around 10 km s ⁻¹ away from the systemic velocity. Molecular line variation is qualitatively similar in all three stars, and it appears that the site of formation is the extended atmosphere. Emission in CO lines tends to be strongest during pulsation phases close to light maximum, and weakest emission or absorption tends to be seen when close to light minimum, resembling the behavior in CN Red and C ₂ Swan system lines at shorter wavelengths. The connection of molecular line variability with the pulsation of the star could be related to a shock that traverses the atmosphere once per pulsation cycle.

Reference : 2026 The Astrophysical Journal, 1006, 104
URL : https://iopscience.iop.org/article/10.3847/1538-4357/ae7a63

Unveiling the enigma of the Nakashima-Deguchi object (IRAS 19312+1950): a candidate Orion KL analog

Gong, Y., Menten, K. M., Kamiński, T., Schuller, F., Navarete, F., Belloche, A., Schilke, P., Wyrowski, F.

The Nakashima-Deguchi object (NDO; aka IRAS 19312+1950) has been recognized as an enigmatic object, exhibiting characteristics of both an evolved star and a star-forming region. However, the actual nature of this object remains a topic of ongoing debate. We conducted observations of this object in (sub)millimeter continuum and molecular line emission using the IRAM-30m and APEX telescopes as well as the SMA. Based on SED fitting of single-dish continuum observations, we determined that the cloud hosting NDO has a dust temperature of $25\pm2$ K, a source-averaged (24$^\prime\prime$) H$_2$ column density of $(4.4\pm 0.6) \times 10^22$ cm$^-2$, a dust emissivity index of $1.7\pm0.2$, and a total gas mass of $220\pm21 M_\odot$. SMA continuum observations resolve the cloud into at least four dust continuum cores. The centrally peaked core MM1, associated with an SiO maser, is the primary mass reservoir. Single-dish spectroscopic observations of NDO led to the detection of 59 spectral lines attributed to 12 species and their isotopologues. This includes the first detection of deuterated molecules, DCO$^+$, DCN, DNC, and HDCO, indicating substantial deuterium abundance. SMA spectroscopic observations detected 75 spectral lines toward MM1, assigned to 12 species and their isotopologues. These lines exhibit diverse morphologies on a scale of $\sim$0.1 pc, likely due to outflow feedback. The observed high-velocity outflow is inconsistent with a spherical morphology and rather resembles a wide-angle bipolar outflow. The presence of deuterated species, and the overall large mass of the complex, the surrounding material of NDO appears more naturally associated with a star-forming environment than with a purely evolved-star scenario. Our investigations led us to postulate that this enigmatic object may represent an Orion KL analog about ten times farther away.

Reference : accepted for publication in A&A
URL : https://arxiv.org/abs/2607.10587

VLT/SPHERE images of the candidate companion of Betelgeuse

Montargès M., Boccaletti A., Flasseur O., de Koter A., Milli J., Kervella P., Ridgway S., Bordier E., Lagadec E., Dupree A. K., Backs F., Calderwood T., Morgan P.

Context. Although the binary fraction of massive main-sequence stars is well established, this is much less so the case for red supergiant (RSG) stars due to the primary’s brightness as well as its complex and strong surface activity.

Aims. Betelgeuse is the most studied RSG. In 2024, through a reinterpretation of its long secondary period (LSP), a close orbiting stellar companion was suggested to exist, with a maximum elongation in December 2024. Our goal with this work was to search for this secondary component.

Methods. We used extreme adaptive optics direct imaging with the Very Large Telescope SPHERE-ZIMPOL instrument by leveraging the pupil tracking mode of the telescope in angular plus spectral differential imaging (ASDI). Image processing was performed through ASDI PAtch Covariances (PACO ASDI) and principal component analysis (PCA).

Results. The candidate Betelgeuse B was detected at 6.1 σ with PACO ASDI and at 5.1 σ with PCA in the CntHa filter on December 6, 2024. The separation is 52.32 ± 0.18 mas, and the position angle is 117.12 ± 0.60°. Assuming the two stars are coeval, the companion is a 2.6 to 3.1 M _⊙ young main-sequence star.

Conclusions. Our observations provide strong evidence that Betelgeuse has a close companion, though formal confirmation that Betelgeuse B is indeed gravitationally bound awaits a second observing epoch. The predicted existence of a companion based on LSP variability and the evidence of the presence of the secondary source reported here identifies LSPs as a potential new avenue for RSG-companion studies, and assessments of their impact on RSG surface and wind structure.

Reference : 2026 Astronomy & Astrophysics, 711, L12
URL : https://www.aanda.org/10.1051/0004-6361/202661023

OH Maser Polarimetric Observations of Planetary Nebulae

Uscanga L., Gray M. D., Gómez J. F., Green J. A., Asanok K., Miranda L. F., Trinidad M. A., Anglada G., Boumis P.

Abstract
We present full-polarization observations of the four ground-state transitions of OH, carried out with the Australia Telescope Compact Array toward two very young planetary nebulae (PNe), IRAS 16333−4807 and IRAS 17393−2727. We detect Zeeman splitting in the 1720 MHz transition in IRAS 16333−4807, with magnetic field strengths of ∼2 to 9 mG, consistent with previous measurements. We also identify a possible reversal in the line-of-sight magnetic field component at −55.7 km s ⁻¹ (previously oriented toward us, now away from us), although this may be affected by spectral blending or variability. For IRAS 17393−2727, we derive magnetic field strengths of ∼3 to 20 mG at 1612 MHz, in agreement with earlier estimates. The linear polarization properties suggest a possible change in the orientation of the sky-plane component of the magnetic field. The data are consistent with variations in the magnetic field configuration in both PNe on timescales of a few years, although higher angular resolution and multiepoch observations are required to confirm this interpretation.

Reference : 2026 The Astrophysical Journal, 1006, 141
URL : https://iopscience.iop.org/article/10.3847/1538-4357/ae80a9

Annoucements

Two Postdoctoral Positions in Unveiling the Interaction Physics of Giant Binary Stars (ERC Advanced Grant SOPHIA)

We are seeking two highly motivated postdoctoral researchers to join the ERC Advanced Grant project SOPHIA, led by Prof. Leen Decin at the Institute of Astronomy of KU Leuven.

SOPHIA aims to transform our understanding of how stars evolve by moving beyond simplified models and accounting for key physical processes such as mass loss, stellar winds, and binary interactions. The project combines cutting-edge observations, advanced modelling, and large datasets, including the upcoming Gaia Data Release 4.

We are recruiting two postdoctoral researchers, each focusing on a complementary aspect of the project:
– Position A: Stellar Winds, Mass Loss, and Radiative Transfer Modelling
– Position B: Binary Star Evolution with Gaia

More information and application instructions on https://fys.kuleuven.be/ster/vacancies/vacancies#PD_SOPHIA

1st announcement: ALMA at 15 years conference open for abstract submissions

1st announcement: ALMA at 15 years conference

Rationale
We are pleased to announce that the international conference "ALMA at 15 Years: Science, Synergies, and the Road Ahead" will be held in person from Feb. 22–26, 2027, at Academia Sinica’s Nangang campus in Taipei, Taiwan. The conference will highlight ALMA’s latest results, especially since the last Pan-ALMA conference held in 2023 and identify exciting directions for future ALMA research.

The program will feature invited and contributed science presentations, along with updates on the Wideband Sensitivity Upgrade (WSU), tutorial sessions on the archival and CARTA systems, and discussions of future ALMA prospects. Talks and posters presenting scientific work using ALMA and/or its synergies with other facilities across all areas of astronomy are welcome. Please visit the official conference website: https://2027alma.org

Important Dates
Abstract Submission Opens: June 15, 2026
Abstract Submission Deadline: September 15, 2026
Early-Bird Online-registration Opens: September 30, 2026
Notification of Abstract Acceptance: Late Oct./Early Nov., 2026
Early Bird Online-registration Deadline: November 27, 2026
Online Registration Deadline: January 20, 2027

SOC
John Carpenter (JAO, Chile), Paola Caselli (MPE, Germany), Marilyn Cruces (UC Chile, Chile), Leen Decin (KU Leuven, Belgium), Maria Diaz Trigo (ESO, Germany), Bunyo Hatsukade (NAOJ, Japan), Rodrigo Herrera-Camus (Universidad de Concepción, Chile), Jongsoo Kim (KASI, Korea), Lihwai Lin (ASIAA, Taiwan; Chair), Leslie Looney (UIUC, USA), Brett McGuire (MIT, USA), Jennifer Donovan Meyer (NRAO/NAASC, USA)

LOC
Cindy Chiu (ASIAA), Tien-Hao Hsieh (TARA), Sheng-Jun Lin (ASIAA), Yu-Nung Su (ASIAA), Ya-Wen Tang (ASIAA), Wei-Hao Wang (ASIAA; Chair)

Contact
Should you have any further inquiries, please feel free to contact the ALMA 2027 Abstract Submission & Registration Office (email: reg@2027alma.org)

We look forward to seeing you in Taipei!

Best regards,
Lihwai Lin (on behalf of SOC)