AAS Meeting #193 - Austin, Texas, January 1999
Session 37. White Dwarfs and Friends
Display, Thursday, January 7, 1999, 9:20am-6:30pm, Exhibits Hall 1

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[37.03] Helium White Dwarf Companions of Field Late-Type Stars

W. Landsman (Raytheon STX), T. Simon (U. of Hawaii)

Helium white dwarfs (HeWDs) are created when the envelope of a red giant is stripped due to the presence of a binary companion. HeWDs with a neutron star companion can be detected as the optical member of a millisecond pulsar (Backer 1998, ApJ, 493, 873). HeWDs with a white dwarf companion can be detected as the brighter member of a double degenerate system (Saffer et al.\ 1998, ApJ, 502, 394). A HeWD with a non-degenerate companion was reported by Landsman et al.\ (1997, ApJ, 481, L93 ), who used ultraviolet spectroscopy to identify the low-mass white dwarf companion of the yellow giant S1040 in the open cluster M67. We have re-analyzed the IUE spectra of known EUV-quiet white dwarf companions of field late-type stars, and used {\em Hipparcos} parallaxes to identify possible HeWDs. The white dwarf companion of the star 39 Cet (G5 III-IV) is a certain HeWD, and the system is a near twin of S1040 in M67. Four other stars (56 Per, HR 3643, HD 160538, and HD 165141) are identified as having possible HeWD companions. We will discuss the feasibility of a empirical determination of the mass-radius relation and envelope mass of these HeWDs.

The author(s) of this abstract have provided an email address for comments about the abstract: landsman@mpb.gsfc.nasa.gov

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