Asteroseismology of the GW Virginis stars SDSS J0349-0059 and VV 47

Abstract

Context. GW Virginis stars are a well-studied class of nonradial g-mode pulsators. SDSS J0349−0059 and VV 47 are two PG 1159 star members of this class of variable stars. SDSS J0349−0059 is an interesting GW Vir star that shows a complete pulsation spectrum that includes rotational splitting of some of its frequencies. VV 47 is a pulsating PG 1159 star surrounded by a planetary nebula. This star is particularly interesting because it exhibits a rich and complex pulsation spectrum.Aims. We present an asteroseismological study of SDSS J0349−0059 and VV 47 aimed mainly at deriving their total mass on the basis of state-of-the-art PG 1159 evolutionary models.Methods. We computed adiabatic nonradial g-mode pulsation periods for PG 1159 evolutionary models with stellar masses ranging from 0.515 to 0.741 M⊙, that take into account the complete evolution of the progenitor stars. We first estimated a mean period spacing for both SDSS J0349−0059 and VV 47 and then constrained the stellar mass of these stars by comparing the observed period spacing with the asymptotic period spacing and with the average of the computed period spacings. We also employed the individual observed periods to search for a representative seismological model for each star. Finally, we estimated the rotation period of SDSS J0349−0059.Results. We found a spectroscopic mass of M⋆ ~ 0.543 M⊙ for SDSS J0349−0059 and M⋆ ~ 0.529 M⊙ for VV 47. By comparing the observed period spacing with the asymptotic period spacing, we obtain M⋆ ~ 0.569 M⊙ for SDSS J0349−0059 and M⋆ ~ 0.523 M⊙ for VV 47. When we compare the observed period spacing with the average of the computed period spacings, we find M⋆ ~ 0.535 M⊙ for SDSS J0349−0059 and M⋆ ~ 0.528 M⊙ for VV 47. Searching for the best period fit, we found for SDSS J0349−0059 an asteroseismological model with M⋆ = 0.542 M⊙ and Teff = 91 255 K. For VV 47, we were unable to find a unique and unambiguous asteroseismological model. Finally, for SDSS J0349−0059, we determined the rotation period to be Prot = 1/Ω ~ 0.407 days.Conclusions. The results presented in this work constitute a further step in the study of GW Vir stars through asteroseismology in the frame of fully evolutionary models of PG 1159 stars. In particular, the potential of asteroseismology to derive stellar masses of PG 1159 stars with an unprecedented precision is shown yet again.