John D. Pritchard

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

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

HV982 a magellanic cloud eclipsing binary star system

Current progress with the Mount John University Observatory Magellanic Cloud eclipsing binary programme is reviewed. A short outline of the programme as a whole is given, and recent observations and reductions and a preliminary analysis of LMC HV982 are presented, including a qualitative description of the problems encountered and their solutions thus far.

Photometry of eclipsing binary stars in the Large and Small Magellanic Clouds

The light curves for three eclipsing binaries in the Magellanic Clouds have been obtained using CCD uVJIC photometry. One target in the LMC, MACHO*05:36:48.7 69:17:00, is an eccentric system, e = 0.20, with a period of 3.853534 0.000005 d. Initial solutions indicate a primary component in the range Te ;1 = 20,000 35,000 K and the secondary Te ;2 1000 2000 K cooler than the primary, with inclinations ranging i = 84.2 86.0 . Two targets in the SMC, MOA J005018.4 723855 and MOA J005623.5 722123, have periods of 1.8399 0.0004 and 2.3199 0.0003 days respectively. Both have circular orbits with the former being a semi-detached system.