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Astron. Astrophys. 320, 913-919 (1997)


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Barium-rich G stars in the nuclei of the planetary nebulae Abell 35 and LoTr5 *

F. Thévenin 1 and G. Jasniewicz 2, 3

1 Observatoire de la Côte d'Azur, B.P. 229, F-06304 Nice Cedex 4, France
2 URA 1280, Observatoire de Strasbourg, 11, rue de l'université, F-67000 Strasbourg, France
3 GRAAL, UPRESA 5024, Université de Montpellier II, CC 72, F-34095 Montpellier Cedex 05, France

Received 14 May 1996 / Accepted 7 October 1996

Abstract

A spectroscopic analysis of the G-star located at the centre of Abell 35 leads to a surface gravity [FORMULA] = 3.7 [FORMULA] and an effective temperature [FORMULA] K, which are typical of a G8IV spectral type. We estimate a projected rotational velocity of [FORMULA] km s-1 and deduce a radius [FORMULA] in agreement with the subgiant luminosity class: the star is rapidly rotating, near the break-up as for LoTr5 (Jasniewicz et al. 1996a). For both late-type central stars of Abell 35 and LoTr5, we show a photospheric enhancement of the barium element which can be understood as caused by the transfer of s-process-overabundant material from the former AGB star which is now the hot star of the binary. These G-stars could be pre-barium stars in detached binary systems.

Key words: planetary nebulae: individual: Abell 35, LoTr5 – stars: binaries – stars: abundances – stars: chemically peculiar

* Based on measurements collected at the European Southern Observatory (La Silla, Chile) and at the Observatoire de Haute Provence (France).

Send offprint requests to: G. Jasniewicz

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998

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