The HST White Dwarf Cooling Sequence of the Old Open Cluster NGC 188


Kurtis A. Williams
E. Jeffery
B. For

Publication Title

American Astronomical Society Meeting Abstracts

Document Type



The white dwarf cooling sequences of open star clusters provide a measurement of stellar systems' ages that are independent of main-sequence age measurements. In addition, recent studies of the white dwarf cooling sequence of the very old and very metal rich open cluster NGC 6791 surprisingly found evidence for multiple populations of white dwarfs, interpreted by different groups as evidence for a binary white dwarf sequence or a helium-core white dwarf cooling sequence, and the resulting white dwarf cooling age estimates. We present the results of a Cycle 16 HST study of white dwarfs in the old, solar-metallicity open cluster NGC 188. Combined with a re-analysis of shallower Cycle 7 data, we compare the white dwarf luminosity function of NGC 188 with that expected from "standard" white dwarf cooling models and that observed in NGC 6791. We also compare the limits on the resultant cluster white dwarf cooling age with ages derived from main sequence fitting.


Physics and Astronomy





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