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Astron. Astrophys. 353, 970-977 (2000)


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Mass-radius relations for white dwarf stars of different internal compositions

J.A. Panei  * , L.G. Althaus  ** and O.G. Benvenuto  ***

Facultad de Ciencias Astronómicas y Geofísicas, Paseo del Bosque S/N, (1900) La Plata, Argentina (panei,althaus,obenvenuto@fcaglp.fcaglp.unlp.edu.ar)

Received 2 March 1999 / Accepted 14 September 1999

Abstract

The purpose of this work is to present accurate and detailed mass-radius relations for white dwarf (WD) models with helium, carbon, oxygen, silicon and iron cores, and with and without a hydrogen envelope, by using a fully updated stellar evolutionary code. We considered masses from 0.15 [FORMULA] to 0.5 [FORMULA] for the case of helium core, from 0.45 [FORMULA] to 1.2 [FORMULA] for carbon, oxygen and silicon cores, and from 0.45 [FORMULA] to 1.0 [FORMULA] for the case of an iron core. In view of the recent measurements made by Hipparcos that strongly suggest the existence of WDs with an iron-dominated core, we focus our attention mainly on the finite-temperature, mass-radius relations for WD models with iron interiors. In addition, we explore the effects of gravitational, chemical and thermal diffusion on low mass helium white dwarf models with hydrogen and helium envelopes.

Key words: stars: evolution – stars: fundamental parameters – stars: interiors – stars: white dwarfs

* Fellow of the Universidad Nacional de La Plata, Argentina
** Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina
*** Member of the Carrera del Investigador Científico, Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Argentina

Send offprint requests to: J. A. Panei

© European Southern Observatory (ESO) 2000

Online publication: January 18, 2000

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