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G117-B15A: How is it Evolving?

Published online by Cambridge University Press:  12 April 2016

S.O. Kepler ,
G. Vauclair ,
R.E. Nather ,
D.E. Winget  and
E.L. Robinson
S.O. Kepler
Affiliation:
Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Brazil
G. Vauclair
Affiliation:
Observatoire Midi-PyreneesFrance
R.E. Nather
Affiliation:
McDonald Observatory and Department of AstronomyThe University of Texasat AustinU.S.A.
D.E. Winget
Affiliation:
McDonald Observatory and Department of AstronomyThe University of Texasat AustinU.S.A.
E.L. Robinson
Affiliation:
McDonald Observatory and Department of AstronomyThe University of Texasat AustinU.S.A.

Abstract

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The measurement of the rate of change of period with time for the g-mode pulsations in ZZ Ceti stars is a direct measurement of the cooling timescale for a DA white dwarf, which in turn can give a totally independent measurement of the age of the galactic disk. Using asteroseismology, we have obtained a rate of change of the period of the dominant pulsation in the light curve of the ZZ Ceti star G117-B15A of dP/dt = (12.5 ± 5.5) × 10−15s/s, equivalent to a timescale for period change of P/P = (5.5 ± 2.4) × 108 yr, which is consistent with the theoretical value for the cooling timescale of a DA white dwarf around 11,000 K.

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 114: White Dwarfs , 1989 , pp. 341 - 345
Copyright
Copyright © Springer-Verlag 1989

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