AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 52. White Dwarfs, Neutron Stars and Pulsars
Display, Tuesday, June 1, 1999, 10:00am-7:00pm, Southeast Exhibit Hall

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[52.01] White Dwarfs in the Globular Cluster NGC 6397

A. M. Cool (San Francisco State University), I. R. King (U.C. Berkeley), J. Anderson (U. C. Berkeley), G. Piotto (Universita di Padova)

We present results of two complementary studies of white dwarfs in the nearby globular cluster NGC 6397 using HST. In the first study, WFPC2 V (F555W) and I (F814W) observations produced a tight sequence of approximately two dozen white dwarfs in a field about 4.5 arcminutes from the cluster center. Here we compare the locus of that observed sequence to model sequences and to field white dwarfs with measured parallaxes. We dicuss the significance of the results for the distance and age of the cluster and for the mass of the white dwarfs currently being formed in the cluster. We also compare the resulting distance to that obtained using field subdwarfs. In the second study, WFPC2 U (F336W) and B (F439W) observations of the cluster center yielded a sequence of close to 100 white dwarfs. Here we compare this sequence to theoretical sequences as a check of the models and of the distance modulus obtained in the V/I study. We also use this sequence to derive a white-dwarf luminosity function which we compare to the theoretical cooling law.

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