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Institut für Astronomie und Astrophysik

Abteilung Astronomie

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Preprint 05/04

Identification of a DO white dwarf and a PG1159 star in the ESO SN Ia progenitor survey (SPY)

K. Werner (1), T. Rauch (1,2), R. Napiwotzki (3), N. Christlieb (4), D. Reimers (4), and C.A. Karl (2)

(1) Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, D-72076 Tübingen, Germany
(2) Dr.-Remeis-Sternwarte, Universität Erlangen-Nürnberg, Sternwartstraße 7, D-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, D-21029 Hamburg, Germany

To be published in: A&A

Abstract. We present high-resolution VLT spectra of a new helium-rich DO white dwarf (HE1314+0018) and a new PG1159 star (HE1429-1209), which we identified in the ESO SPY survey. We performed NLTE model atmosphere analyses and found that the PG1159 star is a low-gravity, extremely hot (Teff =160 000 K, log(g)=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 Teff ~60 000 K, however, the He-II 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.

Preprint (486 kb PDF file including figures)
Astrophysics (astro-ph): astro-ph/0407355

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