Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12666/502
Title: A warm molecular ring in AG Car: composing the mass-loss puzzle
Authors: Bordiu, C.
Bufano, F.
Cerrigone, L.
Umana, G.
Rizzo, J. R.
Buemi, C. S.
Leto, P.
Cavallaro, F.
Ingallinera, A.
Loru, S.
Trigilio, C.
Riggi, S.
Keywords: Stars: evolution;Stars: individual: AG Carina;Stars: Massive;Stars: mass loss;ISM: Abundances;ISM: Molecules
Issue Date: 20-Feb-2021
Publisher: Oxford Academics: Oxford University Press
DOI: 10.1093/mnras/staa3606
Published version: https://academic.oup.com/mnras/article-abstract/500/4/5500/5996198
Citation: Monthly Notices of the Royal Astronomical Society 500(4): 5500–5514(2021)
Abstract: We present APEX observations of CO J = 3 → 2 and ALMA observations of CO J = 2 → 1, 13CO J = 2 → 1, and continuum towards the Galactic luminous blue variable AG Car. These new observations reveal the presence of a ring-like molecular structure surrounding the star. Morphology and kinematics of the gas are consistent with a slowly expanding torus located near the equatorial plane of AG Car. Using non-LTE line modelling, we derived the physical parameters of the gas, which is warm (∼50 K) and moderately dense (∼103 cm−3). The total mass of molecular gas in the ring is 2.7 ± 0.9 M⊙. We analysed the radio continuum map, which depicts a point-like source surrounded by a shallow nebula. From the flux of the point-like source, we derived a current mass-loss rate of M˙=(1.55±0.21)×10−5M⊙ yr−1. Finally, to better understand the complex circumstellar environment of AG Car, we put the newly detected ring in relation to the main nebula of dust and ionized gas. We discuss possible formation scenarios for the ring, namely, the accumulation of interstellar material due to the action of the stellar wind, the remnant of a close binary interaction or merger, and an equatorially enhanced mass-loss episode. If molecular gas formed in situ as a result of a mass eruption, it would account for at least a 30 per cent of the total mass ejected by AG Car. This detection adds a new piece to the puzzle of the complex mass-loss history of AG Car, providing new clues about the interplay between LBV stars and their surroundings.
Description: This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
URI: http://hdl.handle.net/20.500.12666/502
E-ISSN: 1365-2966
ISSN: 0035-8711
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