Volume 636, April 2020
|Number of page(s)||9|
|Section||Stellar structure and evolution|
|Published online||29 April 2020|
Discovery of a complex spiral-shell structure around the oxygen-rich AGB star GX Monocerotis⋆
ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
2 Academia Sinica Institute of Astronomy & Astrophysics (ASIAA), 11F of Astronomy-Mathematics Building, AS/NTU No.1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
3 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago 763 0355, Chile
4 Korea Astronomy and Space Science Institute 776, Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
5 National Science Foundation, 2415 Eisenhower Ave., Alexandria, VA 22314, USA
6 Uppsala University, Department of Physics and Astronomy, Box 516, 75120 Uppsala, Sweden
Accepted: 17 March 2020
The circumstellar envelopes of asymptotic giant branch (AGB) stars exhibit a wide range of morphologies and chemical compositions that can be exploited to unravel their mass-loss history as well as binary status. Here, we present ALMA Band 6 observations centred upon the oxygen-rich, high mass-loss rate AGB star GX Mon. The resulting CO (2–1) map reveals an intricate, complex circumstellar spiral-arc structure consistent with hydrodynamical models for an AGB experiencing mass loss in a highly eccentric, close binary system with an orbital period of around 140 years. Several other transitions (including SiO, SiS, SO2, and CS) are detected in the data, however only the SO (5–4) map shows a similar – although much weaker – distribution as imaged for the CO.
Key words: astrochemistry / stars: AGB and post-AGB / stars: mass-loss / circumstellar matter / submillimeter: stars
This paper makes use of the following ALMA data: ADS/JAO.ALMA#2016.1.00652.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.
© ESO 2020
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