Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...20910310d&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #103.10; Bulletin of the American Astronomical Society,
Astronomy and Astrophysics
Astronomy
Scientific paper
GD 50 is one of the most massive DA white dwarfs known with a mass of 1.2 Msun. Identifying the progenitors of ultra-massive white dwarfs is important as they may set an upper limit on the mass of stars that will evolve into white dwarfs. It has also been suggested that ultra-massive white dwarfs may form through the coalescence of double-degenerate systems. More interest was generated about GD 50 after an observation by the EUVE (Extreme Ultraviolet Explorer) satellite revealed the presence of the Lyman series of singly ionized helium in the extreme-ultraviolet spectrum of GD 50 (Vennes, Bowyer, & Dupuis, 1996, ApJL, 461, 103). Although the helium detected is clearly of photospheric origin, a physical mechanism by which a significant abundance of helium is maintained in the atmosphere of GD 50 has not yet been identified. In order to further investigate the source of helium detected in the atmosphere of GD 50, we present an analysis of the FUSE (Far Ultraviolet Spectroscopic Explorer) spectrum of this ultra-massive white dwarf. The FUV spectrum does not exhibit any metal lines with the exceptions of a few absorption lines associated with gas in the local interstellar medium. We derive stringent upper limits on the abundance of metals, and we discuss whether the non-detection of metals in the atmosphere of GD 50 could rule out the accretion mechanism for explaining the observed helium abundance.
Chayer Pierre
Dupuis Jean
Hénault-Brunet Vincent
Vennes Stephane
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