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Accretion-powered Outflows in AGB Stars

Published online by Cambridge University Press:  30 November 2022

Raghvendra Sahai Open the ORCID record for Raghvendra Sahai [Opens in a new window] ,
Jorge Sanz-Forcada  and
Carmen Sanchez-Contreras Open the ORCID record for Carmen Sanchez-Contreras [Opens in a new window]
Raghvendra Sahai
Affiliation:
Jet Propulsion Laboratory, Pasadena, CA, USA email: [email protected]
Jorge Sanz-Forcada
Affiliation:
Centro de Astrobiologa (CSIC-INTA), ESAC, Villanueva de la Cañada, Madrid, Spain
Carmen Sanchez-Contreras
Affiliation:
Centro de Astrobiologa (CSIC-INTA), ESAC, Villanueva de la Cañada, Madrid, Spain
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Abstract

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One of the big challenges for 21st century stellar astrophysics is the impact of binary interactions on stellar evolution. Such interactions are believed to play a key role in the death throes of 1-8 M⊙ stars, as they evolve from the AGB stars into Planetary Nebulae. X-ray surveys of UV-emitting AGB stars show that ∼40% of objects with FUV emission and GALEX FUV/NUV flux ratios ≳0.2 have variable X-ray emission characterized by very high temperatures (Tx∼35-160 MK) and luminosities (Lx∼0.002-0.2L⊙). We hypothesize that such AGB stars have accretion and (accretion-powered) outflows associated with a close binary companion. UV spectroscopy with HST/STIS of our brightest object (Y Gem) shows the presence of infalling and outflowing gas, providing direct kinematic confirmation of this hypothesis. However, the UV-emitting AGB star population is dominated by objects with little or no FUV emission, and we do not know whether the UV emission from these is intrinsic to the AGB star or extrinsic (i.e., due to binarity). Here we present the first results from a large grid of simple chromospheric models to help discriminate between the intrinsic and extrinsic mechanisms of UV emission for AGB stars.

Keywords

(stars:) circumstellar matter(stars:) binaries (including multiple): closestars: evolutionstars: AGB and post-AGB
Type
Contributed Paper
Information
Proceedings of the International Astronomical Union , Volume 16 , Symposium S366: The Origin of Outflows in Evolved Stars , November 2020 , pp. 246 - 252
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Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
© The Author(s), 2022. Published by Cambridge University Press on behalf of International Astronomical Union

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