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

Year: 2026

Type: article

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

Source: Monthly Notices of the Royal Astronomical Society

DOI: 10.1093/mnras/stag888

Authors: 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, A Zijlstra

Institutions: University of Manchester, National Astronomical Research Institute of Thailand, Centre National de la Recherche Scientifique, Université de Bordeaux, Laboratoire d'Astrophysique de Bordeaux, Monash University, KU Leuven, University of Leeds, Leiden University, Leiden Observatory, Universitat Politècnica de Catalunya, Center for Astrophysics Harvard & Smithsonian, University of Cologne, California Institute of Technology, Jet Propulsion Laboratory, Uppsala University, University College London

Language: English

Topic: Stellar, planetary, and galactic studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,046

Funders: National Science Foundation, National Aeronautics and Space Administration, California Department of Fish and Game, U.S. Nuclear Regulatory Commission, California Institute of Technology, University of Kansas, Scripps Research Institute, U.S. Army Combat Capabilities Development Command Soldier Center, National Astronomical Research Institute of Thailand, European Commission, Deutsche Forschungsgemeinschaft, Agence Nationale de la Recherche, National Science Council, Fonds Wetenschappelijk Onderzoek, Korea Astronomy and Space Science Institute, KU Leuven, Centro de Astrofísica y Tecnologías Afines, National Astronomical Observatory of Japan, Thailand Science Research and Innovation, Agencia Nacional de Investigación y Desarrollo, Jet Propulsion Laboratory, Science and Technology Facilities Council, Australian Research Council, National Institutes of Natural Sciences, Fondo Nacional de Desarrollo Científico y Tecnológico, H2020 European Research Council, Vermont Agency of Natural Resources

OpenAlex ID: W7160702832