Asteroseismology of the DOV star PG 1159−035

Abstract

ABSTRACT Grids of DOV star models are evolved by wdec with fixed atmospheric constituent to the spectral values of XC/XHe/XO = 50/33/17. The core compositions are from white dwarf models at highest Teff evolved by mesa. The eigenfrequencies are calculated and used to fit the observed modes. Based on 264.1 h of photometric observations on PG 1159−035, Winget et al. identified 125 individual frequencies. Costa et al. identified 198 pulsation modes for PG 1159−035 according to the WET photometric data from 1983, 1985, 1989, and 2002. Both of them derived frequency splitting values of δσl = 1 ∼ 4.2 $\mu$Hz and δσl = 2 ∼ 6.9 $\mu$Hz. According to the values of δσl = 1 and δσl = 2, 20 triplets and 9 quintuplets are selected and used to constrain the fitting models. Our optimal model has Teff = 129 000 K, M* = 0.63 M⊙, log g = 7.59, log(Menv/M*) = −5.0, and σRMS = 1.97 s. The values of Teff and log g are consistent with that values of Córsico et al. The calculated modes of minimum rate of period change correspond to modes with maximum kinetic energy distributed in the envelope. The observed rates of period change with positive and negative values can also be partially reproduced. In particular, there are negative rates of period change for the calculated modes from our optimal model, which is not found in previous work.