A high speed camera for photometry of variable objects on the Apache Point Observatory 3.5-m telescope will be constructed and used to undertake several projects related to the pulsation of white dwarf stars. These include: 1) Observations of pulsating massive white dwarfs discovered through the Sloan Digital Sky Survey which will be used (via asteroseismology) to determine whether these stars have crystallized and to what extent. Crystallization plays an important role in determining white dwarf cooling times (which in turn help date the age of the Galaxy and its components) and is also a likely but poorly understood component of the crusts of neutron stars and pulsars. 2) The Sloan Digital Sky Survey has also identified over 150 new cataclysmic variables, some of which contain a pulsating white dwarf. Planned observations of these stars will allow the study of pulsations across a variety of conditions (including accretion and possibly even during outburst) which will in turn be used to probe the interiors of white dwarfs with different evolutionary histories. 3) Ultrashort period (less than 1hour) cataclysmic variables called AM CVn binaries will be searched for among candidates discovered by Sloan. The one known eclipsing AM CVn will be monitored over a long term to measure radii and to search for orbital changes that may be attributed to gravitational radiation. In carrying out this project, a graduate student will be trained in the construction of astronomical instruments and in the science of pulsating white dwarfs. The instrument built here will also be useful for studying astronomical events which occur on short timescales (e.g., flares among magnetically active stars, searching for variability in gamma ray bursts, measuring exo-planetary transits, etc.) and will be made available to all observers using the Apache Point 3.5-meter telescope.
