Identification of a DO white dwarf and a PG 1159 star in the ESO SN Ia progenitor survey (SPY) ^*

¹ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany e-mail: werner@astro.uni-tuebingen.de
² Dr.-Remeis-Sternwarte, Universität Erlangen-Nürnberg, Sternwartstraße 7, 96049 Bamberg, Germany
³ Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
⁴ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany

Received: 24 April 2004
Accepted: 18 May 2004

Abstract

We present high-resolution VLT spectra of a new helium-rich DO white dwarf (HE1314+0018) and a new PG 1159 star (HE1429-1209), which we identified in the ESO SPY survey. We performed NLTE model atmosphere analyses and found that the PG 1159 star is a low-gravity, extremely hot ( = 160 000 K, = 6) star, having a carbon-helium dominated atmosphere with considerable amounts of oxygen and neon (He = 38%, C = 54%, O = 6%, Ne = 2% by mass). It is located within the planetary nebula nuclei instability strip, hence, future searches for an associated PN as well as for stellar pulsations might be successful. The DO white dwarf is a unique object. From the relative strength of neutral and ionized helium lines we found ≈ 60 000 K, however, the lines are extraordinarily strong and cannot be fitted by any model. Similar problems were encountered with hot subdwarfs and white dwarfs showing signatures of a super-hot wind. The reason is unknown.