AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 29. White Dwarfs, Neutron Stars and Pulsars
Oral, Monday, May 31, 1999, 2:00-3:30pm, International Ballroom North

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[29.05] The Faint X-ray Source Population in the Collapsed Core Globular Cluster NGC 6397

J.E. Grindlay, S. Metchev (CfA), A.M. Cool (SF State Univ.)

We have carried out a deep (75ksec) observation with the HRI on ROSAT of the core collapsed globular cluster NGC 6397. This observation (March 1995) greatly extends our initial 15ksec HRI observation of this cluster (Cool et al 1993, ApJ, 410, L103) conducted in March 1991/1992. The same bright sources C1-C3 are detected within ~15arcsec of the cluster core as well as the brighter source ``B" at larger (~30arcsec) offset. However at least one additional point source, C4, is now also detected and at least 2 others are probably required in the central 30arcsec of the cluster to explain the overall distribution of counts in the images. These sources have soft x-ray luminosities Lx ~ 1 - 5 \times 1031 erg/s, and are all apparently time variable over the 2 week total interval of the ROSAT observations. Comparison of the x-ray fluxes with the optical fluxes of the likely counterparts identified in our HST photometry suggests x-ray/optical flux ratios consistent with these objects all being cataclysmic variables and possibly magnetic systems (Grindlay 1999, astro-ph 9901356). The total number of faint x-ray sources and CVs in the cluster located either in x-rays or with HST exceeds 6; our forthcoming much deeper imaging with both HST (H\alpha) and Chandra will probe the complete population.

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