On the Interpretation of High‐Velocity White Dwarfs as Members of the Galactic Halo

A detailed analysis of 32 of the 38 halo white dwarf candidates identified byOppenheimer et al. is presented, based on model atmosphere fits to observedenergy distributions built from optical BVRI and infrared JHK CCD photometry.Effective temperatures and atmospheric compositions are determined for allobjects, as well as masses and cooling ages when trigonometric parallaxmeasurements are available. This sample is combined with that of other halowhite dwarf candidates and disk white dwarfs to study the nature of theseobjects in terms of reduced proper motion diagrams, tangential velocities, andstellar ages. We reaffirm the conclusions of an earlier analysis based onphotographic magnitudes of the same sample that total stellar ages must bederived in order to associate a white dwarf with the old halo population, andthat this can only be accomplished through precise mass and distancedeterminations.Comment: 31 pages, 8 figures, accepted for publication in the Astrophysical Journa