Asteroseismology of the DAV star HS 0507+0434B, including core-composition profiles

Abstract

The DAV star, HS 0507+0434B, was observed by Fu et al. in 2007 and from 2009 December to 2010 January. There were a total of six triplets with nearly equal split, which were identified as l = 1 modes caused by rotation. In order to fit the six l = 1 modes, grids of white dwarf models are generated using the white dwarf evolution code (wdec). For the core-composition profiles, we choose the linear fittings to carbon profile of white dwarf models from modules for experiments in stellar astrophysics (mesa), which can be considered as the results of the real nuclear-burning process. Coupled with diffusion equilibrium H/He and He/C mixtures, we make grids of models in wdec and perform asteroseismology of HS 0507+0434B. There is a total error of 9.50 s for our best-fitting model, which is smaller than the result of Fu et al. (i.e. a total error of 22.1 s), when fitting the six l = 1 modes. The two other previously identified pulsation mode frequencies (286.1 and 743.40 s) can also be well fitted by our best-fitting model. The model parameters are Teff = 11 450 K, log g = 8.088, M* = 0.640 M⊙, log (MH/M*) = −6 and log (MHe/M*) = −3.