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FUV Emission from AGB Stars: Modeling Accretion Activity Associated with a Binary CompanionIt is widely believed that the late stages of evolution for Asymptotic Giant Branch (AGB) stars are influenced by the presence of binary companions. Unfortunately, there is a lack of direct observational evidence of binarity. However, more recently, strong indirect evidence comes from the discovery of UV emission in a subsample of these objects (fuvAGB stars). AGB stars are comparatively cool objects (< or =3000 K), thus their fluxes falls off drastically for wavelengths 3000 Angstroms and shorter. Therefore, ultraviolet observations offer an important, new technique for detecting the binary companions and/or associated accretion activity. We develop new models of UV emission from fuvAGB stars constrained by GALEX photometry and spectroscopy of these objects. We compare the GALEX UV grism spectra of the AGB M7 star EY Hya to predictions using the spectral synthesis code Cloudy, specifically investigating the ultraviolet wavelength range (1344-2831 Angstroms). We investigate models composed of contributions from a photoionized "hot spot" due to accretion activity around the companion, and "chromospheric" emission from collisionally ionized plasma, to fit the UV observations.
Document ID
20150005613
Acquisition Source
Jet Propulsion Laboratory
Document Type
Other
External Source(s)
Authors
Stevens, Alyx Catherine
(Texas Univ. San Antonio, TX, United States)
Sahai, Raghvendra
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
April 13, 2015
Publication Date
December 21, 2012
Subject Category
Astrophysics
Distribution Limits
Public
Copyright
Other
Keywords
ultraviolet emission
accretion
binarity
mass-loss
Asymptotic Giant Branch (AGB) stars

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