Lyman Spectroscopy of Hot DA White Dwarfs

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Session 30 -- First Results from Astro 2
Oral presentation, Tuesday, June 13, 1995, 2:00pm - 5:30pm

[30.03] Lyman Spectroscopy of Hot DA White Dwarfs

David S. Finley (Eureka Scientific, Inc.)

Several hot (\teff\ $>$ 20,000 K) DA white dwarfs were observed with the Hopkins Ultraviolet Telescope (HUT) during the recent ASTRO-2 mission. This is the first time that the full hydrogen Lyman series has been observed for a significant number of white dwarfs. The observations were undertaken as a critical test of Stark broadening theory and the Hummer-Mihalas occupation probability formalism (Hummer, D.G. and Mihalas, D. 1988, ApJ 331, 794); any departures were expected to be of much greater magnitude in the Lyman lines, given that they are much stronger than the Balmer lines. To span the widest possible range in \teff\ and \logg\, the targets included Wolf 1346, GD 50, GD 71, GD 153, GD 394, RE0512-004, RE1738+669, HZ 43, and G191-B2B. These include one of the coolest DA without Lyman satellite features, Wolf 1346 (20,000 K), and the hottest known DA, RE1738+669 (95,000 K); one of the least massive DA, RE0512-004 (\logg\ = 7.3), and the most massive known DA, GD 50 (\logg\ = 9.2). (The temperatures and gravities listed are from pure H model fits to our optical spectra). The flight data are now being reduced, after which we will perform detailed comparisons of the Lyman and Balmer line profiles with models. We will be reporting on the initial results of that comparison.

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