Seismology of the Accreting White Dwarf in GW Librae

Abstract

We present a first analysis of the g-mode oscillation spectrum for the white dwarf (WD) primary of GW Lib, a faint cataclysmic variable. Stable periodicities have been observed from this WD for a number of years, but their interpretation as stellar pulsations has been hampered by a lack of theoretical models appropriate to an accreting WD. Using the results of Townsley & Bildsten, we construct accreting models for the observed effective temperature and approximate mass of the WD in GW Lib. We compute g-mode frequencies for a range of accreted layer masses, Macc, and long-term accretion rates, 〈M〉. If we assume that the observed oscillations are from Script l sign = 1 g-modes, then the observed periods are matched when M ≈ 1.02 M ⊙, Macc ≈ 0.31 × 10-4 M ⊙, and 〈M〉 7.3 × 10-11 M ⊙ yr-1. Much more sensitive observations are needed to discover more modes, after which we will be able to more accurately measure these parameters and constrain or measure the WD's rotation rate.