Outer convection zones and internal temperatures of cool white dwarfs |
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| Authors: | Karl-Heinz Böhm |
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| Institution: | (1) Astronomy Department, University of Washington, Seattle, Wash., USA |
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| Abstract: | The outer convection zone of the low-temperature white dwarf Van Maanen 2 has been studied for two different atmospheric models given byWeidemann (1960). A slight modification of the standard mixing length theory and the abundances derived by Weidemann have been used.The thickness of the convection zone is about 8 km for the atmospheric model withT
eff=5780 K,g=108 cm sec–2 and about 23 km forT
eff=5040,g=3.16×107K. In both cases the temperature at the lower boundary of the convection zone is about 9.8×105K. It is shown that this temperature corresponds approximately to the transition temperatureT
tr to the (almost) isothermal core of the white dwarf. This value is considerably lower than the values ofT
tr discussed in the literature until now.The outer convection zone consists of an upper completely non-degenerate part and a lower part with moderate degeneracy. In this lower part the degree of degeneracy is practically independent of depth. |
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