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Issue A&A
Volume 453, Number 3, July III 2006
Page(s) 1051 - 1057
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20064843



A&A 453, 1051-1057 (2006)
DOI: 10.1051/0004-6361:20064843

The accretion-diffusion scenario for metals in cool white dwarfs

D. Koester and D. Wilken

Institut für Theoretische Physik und Astrophysik, University of Kiel, 24098 Kiel, Germany
    e-mail: koester@astrophysik.uni-kiel.de

(Received 11 January 2006 / Accepted 31 January 2006 )

Abstract
We calculated diffusion timescales for Ca, Mg, Fe in hydrogen atmosphere white dwarfs with temperatures between 5000 and 25 000 K. With these timescales we determined accretion rates for a sample of 38 DAZ white dwarfs from the recent studies of Zuckerman et al. (2003, ApJ, 596, 477) and Koester et al. (2005, A&A, 432, 1025). Assuming that the accretion rates can be calculated with the Bondi-Hoyle formula for hydrodynamic accretion, we obtained estimates for the interstellar matter density around the accreting objects. These densities are in good agreement with new data about the warm, partially ionized phase of the ISM in the solar neighborhood.


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



© ESO 2006


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