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Rate of change of the pulsation periods in the PG 1159 star PG 0122+200

Published online by Cambridge University Press:  01 April 2008

G. Vauclair ,
J.-N. Fu ,
J.-E. Solheim ,
S.-L. Kim ,
M. Chevreton ,
N. Dolez ,
L. Chen ,
M. A. Wood  and
I. M. Silver
G. Vauclair
Affiliation:
Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 av. E. Belin, 31400 Toulouse, France
J.-N. Fu
Affiliation:
Department of Astronomy, Beijing Normal University, Beijing 100875China
J.-E. Solheim
Affiliation:
Institute of Theoretical Astrophysics, University of Oslo, Oslo, Norway
S.-L. Kim
Affiliation:
Korea Astronomy and Space Science Institute, Daejeon, Korea
M. Chevreton
Affiliation:
LESIA, Observatoire de Paris-Meudon, Meudon, France
N. Dolez
Affiliation:
Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 av. E. Belin, 31400 Toulouse, France
L. Chen
Affiliation:
Department of Astronomy, Beijing Normal University, Beijing 100875China
M. A. Wood
Affiliation:
Department of Physics and Space Sciences & SARA Observatory, Florida Institute of Technology, Florida 32935, USA
I. M. Silver
Affiliation:
Department of Physics and Space Sciences & SARA Observatory, Florida Institute of Technology, Florida 32935, USA
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Abstract

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The pre-white dwarf pulsators of PG 1159 type, or GW Virginis variable stars, are in a phase of rapid evolution towards the white dwarf cooling sequence. The rate of change of their nonradial g-mode frequencies can be measured on a reasonably short time scale. From a theoretical point of view, it was expected that one could derive the rate of cooling of the stellar core from such measurements. At the cool end of the GW Virginis instability strip, it is predicted that the neutrinos flux dominates the cooling. PG 0122+200 which defines the red edge of the instability strip is in principle a good candidate to check this prediction. It has been followed-up through multisite photometric campaigns for about fifteen years. We report here the first determination of the rate of change of its 7 largest amplitude frequencies. We find that the amplitudes of the frequency variations are one to two orders of magnitude larger than predicted by theoretical models based on the assumption that these variations are uniquely caused by cooling. The time scales of the variations are much shorter than the ones expected from a neutrino dominated core cooling. These results point to the existence of other mechanisms responsible for the frequency variability. We discuss the role of nonlinearities as one possible mechanism.

Keywords

neutrinosstars:evolutionstars: individual (PG 0122+200)stars: oscillationsstars: white dwarfs
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Symposium S252: The Art of Modeling Stars in the 21st Century , April 2008 , pp. 157 - 162
Copyright
Copyright © International Astronomical Union 2008

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