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Session 76 - Cataclysmic Variables and Accretion Disks.
Display session, Wednesday, January 15
We present results of an HST WFPC2 photometric study of cataclysmic variables, white dwarfs, and other UV-bright stars in the central regions of the core-collapsed globular cluster NGC 6397. Three previously identified cataclysmic variables are found to flicker in a 16 hour time series obtained in HST U and B filters. A fourth and fainter CV candidate has been identified based on its photometric variability and excess UV emission. Three additional faint UV-bright objects near the center of the cluster appear to represent a separate class of centrally concentrated objects, showing no variability and broad-band UBVI colors significantly different from the CVs. Three blue stragglers are found to be variable stars with light curves that suggest one is a probable W UMa binary and another is a possible pulsator. Finally, we identify an extended white dwarf sequence containing approximately 100 stars, and compare it to theoretical models of DA and DB white dwarfs.
Program listing for Wednesday