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The Spectra and Colors of Cool White Dwarfs

Published online by Cambridge University Press:  12 April 2016

M. S. Bessell ,
D. T. Wickramasinghe  and
P. L. Cottrell
M. S. Bessell
Affiliation:
Australian National University
D. T. Wickramasinghe
Affiliation:
Australian National University
P. L. Cottrell
Affiliation:
Australian National University

Extract

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White dwarfs fall in two main categories (1) the group with H-rich atmospheres (DA) the most numerous, and (2) the group with He-rich atmospheres (DB, DC, DF, DG, λ4670). Calculations of element separation (via gravitational settling) and convective mixing in white dwarf models have been made by Koester (1976) and Vauclair and Reisse (1977) in order to understand the existence and maintenance of these distinct groups and to predict at what stage during the cooling of the white dwarf some connection may occur between the two groups. Over the last few years, Wickramasinghe, Bessell and Cottrell (Wickramasinghe et al., 1977; Cottrell et al., 1977; Bessell and Wickramasinghe, 1979; Bessell, 1978 and Wickramasinghe and Bessell, 1979) have investigated the properties of cool (T < 6000K white dwarfs observationally and theoretically. We have attempted to establish at what temperature mixing does occur in DA white dwarfs, whether cool white dwarfs could be confused with G, K and M dwarfs, and if one can discriminate spectroscopically cool He and H-rich white dwarfs. In this paper we will discuss the spectra and colors of the coolest (Te < 5000K white dwarfs and compare them with model atmosphere calculations.

Type
Colloquium Session III
Information
International Astronomical Union Colloquium , Volume 53: White Dwarfs and Variable Degenerate Stars , August 1979 , pp. 179 - 183
Copyright
Copyright © The University of Rochester 1979

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