The non-radially pulsating primary of the cataclysmic variable GW Librae

Abstract

ABSTRACT The dwarf nova GW Librae is the first cataclysmic variable dis covered to have a primary in awhite dwarf instability strip, making it the first multi-mode, nonradially-pulsatingstar knownto be accreting. The primaries of CVs, embedded in hot, bright accretion discs, are difficultto study directly. Applying the techniques of asteroseismology to GW Librae could thereforegive us an unprecedented look at a white dwarf that has undergone ∼ 10 9 years of accretion.However, an accreting white dwarf may have characteristics sufficiently different from thoseof single pulsating white dwarfs to render the standard models of white dwarf pulsations in-valid for its study.This paper presents amplitudespectra of GW Lib from a series of observingcampaignsconductedduring1997,1998and 2001.We find that t he dominantpulsationmodescluster at periods near 650, 370 and 230 s, which also appear in linear combinations with eachother. GW Lib’s pulsation spectrum is highly unstable on time-scales of months, and exhibitsclusters of signals very closely spaced in frequency, with separations on the order of 1 µHz.Key words: Stars: cataclysmic variables, white dwarfs, oscillations – Individual: GW Librae