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19. Convection Zones and Coronae of White Dwarfs

Published online by Cambridge University Press:  14 August 2015

K. H. Böhm  and
J. Cassinelli
K. H. Böhm
Affiliation:
Astronomy Dept., University of Washington, Seattle, Wash., U.S.A.
J. Cassinelli
Affiliation:
Astronomy Dept., University of Washington, Seattle, Wash., U.S.A.

Abstract

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Outer convection zones of white dwarfs in the range 5800 K ≤ Teff ≤ 30000 K have been studied assuming that they have the same chemical composition as determined by Weidemann (1960) for van Maanen 2. Convection is important in all these stars. In white dwarfs Teff < 8000 K the adiabatic temperature gradient is strongly influenced by the pressure ionization of H, HeI and HeII which occurs within the convection zone. Partial degeneracy is also important.

Convective velocities are very small for cool white dwarfs but they reach considerable values for hotter objects. For a white dwarf of Teff = 30000 K a velocity of 6.05 km/sec and an acoustic flux (generated by the turbulent convection) of 1.5 × 1011 erg cm−2 sec−1 is reached. The formation of white dwarf coronae is briefly discussed.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 42: White Dwarfs , 1971 , pp. 130 - 135
Copyright
Copyright © Reidel 1971 

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