Two Confirmed Cataclysmic Variables in the Old Stellar Cluster NGC 6791

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Abstract
Based on new CCD photometry and spectroscopy we confirm the presence of two cataclysmic variables (CVs) in the very old open cluster NGC 6791. One of these variables, known as B8, was observed by Rucinski, Kaluzny, & Hilditch to undergo a large-magnitude outburst in 1995. The spectrum of this star outside the outburst, obtained by us with Multiple Mirror Telescope, clearly shows emission lines characteristic of dwarf novae. We observed the second star, known as B7, to undergo a large (~3 mag) drop in its brightness over ~10 days. The spectrum of B7 obtained in the high state resembles spectra of nova-like CVs. This star is likely a member of the UX UMa subtypes of CVs. Variables B7 and B8 represent only the second and the third cataclysmic variables known in open clusters. Variable B7 has observational characteristics that would make it difficult to identify as a CV with some of the methods currently being used in surveys for CVs in globular clusters.
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