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Preprint 08a/06

Soft X-ray Spectroscopy of the Hot DA White Dwarf LB1919 and the PG1159 Star PG1520+525

K. Werner (1), J. J. Drake (2), T. Rauch (1), S. Schuh (3), and A. Gautschy (4)

(1) Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
(2) Harvard-Smithsonian Center for Astrophysics, MS 3, 60 Garden Street, Cambridge, MA 02138, USA
(3) Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
(4) Wetterchrüzstr. 8c, 4410 Liestal, Switzerland

To be published in: ASP Conf. Series, Proceedings of the 15th European Workshop on White Dwarfs

Abstract. We have performed soft X-ray spectroscopy of two hot white dwarfs with the Chandra observatory using the Low Energy Transmission Grating. The first target is the hot DA white dwarf LB1919 (T_eff=69 000 K). This star is representative of a small group of hot DAs whose metallicities lie well below predictions from radiative levitation theory. The Chandra spectrum shows a rich absorption line spectrum which may allow to find the origin of the low-metallicity nature of these DAs. The second target is PG1520+525, a very hot non-pulsating PG1159 star. We find that it is hotter (T_eff=150 000 K) than the pulsating prototype PG1159-035 (T_eff=140 000 K) and conclude that both stars confine the blue edge of the GW Vir instability strip.
 

Preprint (232 kb PDF file including figures)
Astrophysics (astro-ph): astro-ph/0610013

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