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Strong Variable Ultraviolet Emission from Y Gem: Accretion Activity in an Asymptotic Giant Branch Star with a Binary Companion?

Sahai, Raghvendra and Neill, James D. and Gil de Paz, Armando and Sánchez Contreras, Carmen (2011) Strong Variable Ultraviolet Emission from Y Gem: Accretion Activity in an Asymptotic Giant Branch Star with a Binary Companion? Astrophysical Journal Letters, 740 (2). Art. No. L39. ISSN 2041-8205. http://resolver.caltech.edu/CaltechAUTHORS:20111207-134126683

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Abstract

Binarity is believed to dramatically affect the history and geometry of mass loss in asymptotic giant branch (AGB) and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to look for hot binary companions to cool AGB stars using the Galaxy Evolution Explorer archive, we have discovered a late-M star, Y Gem, to be a source of strong and variable UV emission. Y Gem is a prime example of the success of our technique of UV imaging of AGB stars in order to search for binary companions. Y Gem's large and variable UV flux makes it one of the most prominent examples of a late-AGB star with a mass accreting binary companion. The UV emission is most likely due to emission associated with accretion activity and a disk around a main-sequence companion star. The physical mechanism generating the UV emission is extremely energetic, with an integrated luminosity of a few × L_☉ at its peak. We also find weak CO J = 2-1 emission from Y Gem with a very narrow line profile (FWHM of 3.4 km s^(–1)). Such a narrow line is unlikely to arise in an outflow and is consistent with emission from an orbiting, molecular reservoir of radius 300 AU. Y Gem may be the progenitor of the class of post-AGB stars which are binaries and possess disks but no outflows.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/2041-8205/740/2/L39DOIArticle
http://iopscience.iop.org/2041-8205/740/2/L39/PublisherArticle
ORCID:
AuthorORCID
Neill, James D.0000-0002-0466-1119
Additional Information:© 2011 The American Astronomical Society. Received 2011 July 15; accepted 2011 August 6; published 2011 September 28. We thank the staff of the Arizona Radio Observatory for granting us observing time. We thank Noam Soker and Joel Kastner for their valuable comments on an earlier version of this Letter. R.S.’s contribution to the research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Financial support was provided by NASA through a Long Term Space Astrophysics and GALEX GO award.
Group:Space Astrophysics Laboratory
Funders:
Funding AgencyGrant Number
NASAUNSPECIFIED
GALEX GO awardUNSPECIFIED
Subject Keywords:accretion, accretion disks; binaries: general; circumstellar matter; stars: AGB and post-AGB; stars: individual (Y Gem, Mira); stars: mass-loss
Record Number:CaltechAUTHORS:20111207-134126683
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20111207-134126683
Official Citation: Strong Variable Ultraviolet Emission from Y Gem: Accretion Activity in an Asymptotic Giant Branch Star with a Binary Companion? Raghvendra Sahai et al. 2011 ApJ 740 L39
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28355
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:07 Dec 2011 22:09
Last Modified:22 May 2017 23:21

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