A&A 451, 147-155 (2006)
DOI: 10.1051/0004-6361:20053769

DQ white-dwarf stars with low C abundance: possible progenitors

C. G. Scóccola¹, L. G. Althaus¹, A. M. Serenelli², R. D. Rohrmann³ and A. H. Córsico<sup>1

1</sup>  Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, s/n, (1900) La Plata, Argentina Instituto de Astrofísica La Plata, IALP, CONICET
    e-mail: [cscoccola;althaus;acorsico]@fcaglp.unlp.edu.ar
²  Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ, 08540, USA
    e-mail: aldos@ias.edu
³  Observatorio Astronómico, Universidad Nacional de Córdoba, Laprida 854, (5000) Córdoba, Argentina
    e-mail: rohr@oac.uncor.edu

(Received 5 July 2005 / Accepted 1 December 2005)

Abstract
Aims.The present paper focuses on the evolution of hydrogen-deficient white dwarfs with the aim of exploring the consequences of different initial envelope structures on the carbon abundances expected in helium-rich, carbon-contaminated DQ white dwarfs. In particular, the evolutionary link between the DQs with low detected carbon abundances and the PG 1159, extreme horizontal branch, and helium-rich R Coronae Borealis (RCrB) stars is explored.
Methods.We present full evolutionary calculations that take a self-consistent treatment of element diffusion into account as well as expectations for the outer layer chemical stratification of progenitor stars upon entering the white dwarf regime.
Results.We find that PG 1159 stars cannot be related to any DQ white dwarfs with low C abundances. Instead, we suggest that the latter could constitute the progeny of the giant, helium-rich RCrB stars.

Key words: stars: evolution -- stars: interiors -- stars: white dwarfs -- stars: abundances

SIMBAD Objects

© ESO 2006

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

• If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
• You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
• You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.