STRONG VARIABLE ULTRAVIOLET EMISSION FROM Y GEM: ACCRETION ACTIVITY IN AN ASYMPTOTIC GIANT BRANCH STAR WITH A BINARY COMPANION?

Journal Article · Thu Oct 20 00:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/740/2/L39· OSTI ID:21565374

Sahai, Raghvendra ^[1]; Neill, James D ^[2]; Gil de Paz, Armando ^[3]; Sanchez Contreras, Carmen ^[4]

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1. Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States)
2. California Institute of Technology, 1200 E. California Blvd. MC278-17, Pasadena, CA 91125 (United States)
3. Dpto. de Astrofisica, Universidad Complutense de Madrid, E-28040 Madrid (Spain)
4. Astrobiology Center (CSIC-INTA), ESAC campus, E-28691 Villanueva de la Canada, Madrid (Spain)

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 x L{sub sun} 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{sup -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.

• OSTI ID: 21565374
• Journal Information: Astrophysical Journal Letters, Vol. 740, Issue 2; Other Information: DOI: 10.1088/2041-8205/740/2/L39; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
BINARY STARS
CARBON MONOXIDE
EMISSION
GALACTIC EVOLUTION
GIANT STARS
LOSSES
MASS
ULTRAVIOLET RADIATION
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
ELECTROMAGNETIC RADIATION
EVOLUTION
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
STARS