Monitoring variable white dwarfs with WASP

Faedi, F.; West, R. G.; Burleigh, M.; Goad, M.; Christian, D.; Clarkson, W. I.; Collier Cameron, A.; Evans, A.; Haswell, C. A.; Hellier, C.; Horne, K.; Irwin, J.; Kane, S.; Lister, T.; Norton, A. J.; Pollacco, D.; Skillen, I.; Street, R. and Wheatley, P. (2007). Monitoring variable white dwarfs with WASP. In: 15th European Workshop on White Dwarfs, 7-11 Aug 2006, Leicester, United Kingdom..



The SuperWASP project is an ultra wide angle search for extra solar planetary transits. However SuperWASP can also be used extensively for monitoring variable stars. Most white dwarfs are thought to be stable photometrically and are often used as calibration standards for optical and ultra-violet observations. However, a few white dwarfs are intrinsically variable. For example, the ZZ Ceti stars are non-radial pulsators with variability time scales of a few hundred seconds. White dwarfs in close, detached binaries, often display optical variability such as eclipses, from which radii can be determined, or the effects of reflection and irradiation on a low mass companion. Rare magnetic white dwarfs often display star-spots which rotate in and out of view, revealing the spin period of the star. SuperWASP will monitor several hundred white dwarfs brighter than ˜14th magnitude on time scales from 10 minutes to months. The majority of these stars have never previously been tested for photometric variability. These observations will reveal new close binary systems, particularly those with optically undetectable very low mass (brown dwarf) companions, and enable us to determine spin periods in magnetic degenerates, some of which are thought to have periods of months--years.

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