A new white dwarf constraint on the rate of change of the gravitational constant

Abstract

In this paper we derive a new bound on the rate of change of the gravitational constant G coming from the pulsating white dwarf G117-B15A. This star is a ZZ Ceti pulsator extensively studied with astroseismological techniques for last three decades. The most recent determination of {\dot P} for the 215.2 s fundamental mode agrees very well with predictions of the best fit theoretical model. The rate of change of the oscillation period can be translated to the cooling speed of the star. Since the evolution of such stars is governed by surface photon emission and residual gravitational contraction, any change in $G$ would modify the cooling process. Therefore observational determination of the cooling speed can be used to set the upper bound on the rate of change of G. In the light of the current data concerning G117-B15A we derive the bound which is one of the most stringent bounds obtained for {\dot G} so far.