AAS 201st Meeting, January, 2003
Session 119. White Dwarfs
Poster, Thursday, January 9, 2003, 9:20am-4:00pm, Exhibit Hall AB

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[119.06] A Dynamical Mass for the Hot, White Dwarf Companion in HR 1608: Testing the Models for Helium-Core White Dwarfs

K. M. Sandstrom (Department of Astronomy, Harvard University), D. W. Latham, G. Torres (Harvard-Smithsonian Center for Astrophysics), W. B. Landsman (NASA/GSFC/SSAI), R. P. Stefanik (Harvard-Smithsonian Center for Astrophysics)

A spectroscopic orbit for the binary system HR 1608 has been obtained using the 1.5m Wyeth telescope at Oak Ridge Observatory. ROSAT and IUE observations have shown that this system contains a hot, white dwarf companion. Making use of the new radial velocity orbit, we attempt to derive a dynamical mass for the white dwarf in this system. For a single-lined spectroscopic orbit, this requires the mass function from the spectroscopic orbit, the inclination of the orbital plane and either the mass ratio or the mass of the primary star in the system. The inclination of the orbital plane is found by combining the spectroscopic orbit with an astrometric orbit calculated from the Hipparcos Intermediate Data. Yale isochrones are used to find the mass of the primary star. We find a dynamical mass of 0.389 ± 0.019 M\odot for the white dwarf companion in HR 1608, indicating that the white dwarf has a helium core. The agreement between mass-radius models for helium core white dwarfs and the dynamical mass and radius, calculated from fits to the ultraviolet spectrum, is discussed. We find that the mass and radius are consistent, to within the observational errors, with Dreibe et al (1998) He-core models at a temperature of 25,000 K, very close to the temperature of 24,725 ± 125 K found from model atmosphere fits to the UV spectrum.

The author(s) of this abstract have provided an email address for comments about the abstract: karin@astron.berkeley.edu

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