Effective Temperatures and Surface Gravities for DA White Dwarfs in Wide Binaries

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Session 50 -- White Dwarfs
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

[50.05] Effective Temperatures and Surface Gravities for DA White Dwarfs in Wide Binaries

M.M.Martinez, T.D.Oswalt (Florida Tech)

Using a novel multiple-dimensional cubic splines interpolation program devised by Penton (1990; M.S. thesis, Fl.Tech.) and an extensive grid of atmospheric models supplied by Koester (1990; priv. comm.) we have estimated effective temperatures and surface gravities for a sample of new spectroscopically identified white dwarfs (WDs) with hydrogen-rich atmospheres. Most of these WDs are members of common proper motion binary systems discovered during the Luyten and Giclas proper motion surveys. The observational data consists of Balmer line equivalent width measurements derived from low-resolution digital spectra obtained at the KPNO and CTIO 4-m telescopes between January 1988 and November 1990. Uncertainties for the derived effective temperatures and surface gravities were determined directly from the signal-to-noise ratio of the spectra. Since most of these objects have no previous spectroscopic observations, a comparison of our results with previously published values is restricted to a smaller subset of the sample and to WDs that were used as flux standards. From this comparison we have determined that the effective temperatures and spectral subclasses we derived for the WDs agree with the available literature values quite well. However the estimated surface gravities seem to be consistently higher than the literature values. Details of the method and its limitations will be presented. This research was supported by NSF grant AST9016284 to Florida Institute of Technology.

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