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Preprint 08/11

Spectral Analysis of the O(He)-Type Central Stars of the Planetary Nebulae K1-27 and LoTr 4

N. Reindl (1), E. Ringat (1), T. Rauch (1), K. Werner (1), J. W. Kruk (2)

(1) Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, 72076 Tuebingen, Germany
(2) NASA Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.

To be published in: Proceedings IAU Symposium No. 283, 2011

Abstract. The four known O(He) stars are the only amongst the hottest post-AGB stars whose atmospheres are composed of almost pure helium. Thus, their evolution deviates from the hydrogen-deficient post-AGB evolutionary sequence of carbon-dominated stars like e.g. PG 1159 stars. The origin of the O(He) stars is still not explained. They might be either post-early AGB stars or the progeny of R Coronae Borealis stars. We present preliminary results of a non-LTE spectral analysis based on FUSE and HST/COS observations.
 
Key words: abundances, AGB and post-AGB, atmospheres, evolution, planetary nebulae: individual (K 1-27, LoTr 4)

Preprint (532 kb PDF file including figures)

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