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A.S. Mukadam, P. Szkody (University of Washington, Seattle WA 98195), B. T. Gansicke (University of Warwick, Coventry CV4 9BU, UK), B. Warner, P. Woudt (University of Cape Town, Rondebosch 7700, South Africa), E. Sion (Villanova University, Villanova, PA 19085), D. Townsley, L. Bildsten (Univ. of California, Santa Barbara, CA 93106), J. E. Solheim (University of Oslo, Blindern, Oslo, Norway), O. Fraser, D. Haggard (University of Washington, Seattle WA 98195)
Most cataclysmic variables do not eclipse and are thus difficult to study. With the recent discovery of pulsating white dwarfs in cataclysmic variables (see Warner & van Zyl 1998; van Zyl et al. 2000), we can use the technique of asteroseismology to study these objects. A unique model fit to the observed periods of the pulsating white dwarf contains information about the stellar mass, core composition, age, rotation rate, magnetic field strength, and distance (e.g. Winget et al. 1998). Characterizing such systems will help us grasp the effect of accretion on pulsations, important for all pulsating stars.
Our preliminary observations using the 3.5m telescope at Apache Point Observatory suggest the discovery of two new pulsating white dwarfs among the cataclysmic variables of the Sloan Digital Sky Survey: WD0745+4538 and WD2143+1244. Precise measurements of periods requires a long time-base, but our present succinct light curve on WD0745+4538 indicates periods near 1010s and 647s with amplitudes of 6.6% and 5.7% respectively. Our hour-long light curve on WD2143+1244 shows a period at 616s with an amplitude of 0.8%. These periods are within the expected range for non-radial g-mode pulsations in white dwarfs.
We have acquired ultra-violet (UV) time resolved spectroscopy of the previously discovered pulsating accreting white dwarfs WD0131-0901, WD1610-0102, and WD2205+1155 (Woudt & Warner 2004; Warner & Woudt 2004) using the Advanced Camera for Surveys mounted on the Hubble Space Telescope (HST). We intend to determine the effective temperature of these variables in order to better define the instability strip for accreting pulsating white dwarfs (Szkody et al. 2002). We also obtained multi-site optical observations of WD1610-0102 from the ground simultaneously with the HST campaign. We hope to utilize the UV and optical amplitudes to attempt a mode identification for the observed periodicities of WD1610-0102.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.