Collaborative Research on Study of Halo Cataclysmic Variables

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Cataclysmic variables (CVs) are stellar systems that are characterized by sudden brightness changes. They include novae and nova-like variables. All CVs are close binary stars, consisting of a compact object, usually a white dwarf, and a red star. CVs are found among the disk and the halo population of stars in our Galaxy. The Principal Investigators* (PIs) propose to observe photo- metrically and spectroscopically 40 to 50 CVs that are candidate members of the halo population of our galaxy. The chief observing tool will be two-dimensional charge-coupled devices (CCDs), which will allow accurate photometric studies despite the objects' extreme faintness. The goal of this research is to determine the orbital and physical properties of halo CVs and to compare them with data of galactic disk CVs. The results of this observational program and of other CV systems already in the literature should provide information on how age, chemical composition, and parent population affect the formation of binary stars and, in particular, CVs. The PIs expect to be able to choose between conflicting theories on the properties and formation of CVs. This proposal is one of three identical proposals, each with its own budget, submitted by Principal Investigators (PIs) from three different institutions. The other two PIs are Steven Howell of the Planetary Science Institute (NSF Proposal 8914866) and Joseph Patterson of Columbia University (8916995).