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Session 76 - Cataclysmic Variables and Accretion Disks.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[76.03] HST Observations of Cataclysmic Variables, White Dwarfs, and Other UV-Bright Stars in the Globular Cluster NGC 6397

A. M. Cool (San Francisco State U.), C. Sosin, I. R. King (U.C. Berkeley), H. N. Cohn, P. M. Lugger (Indiana U.), C. D. Bailyn (Yale U.), J. E. Grindlay (Harvard U.)

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