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SUMMARY:Photometric constraints on white dwarfs and the identification of 
 extreme objects - Daniel J. Mortlock\, Imperial College London
DTSTART:20090216T160000Z
DTEND:20090216T170000Z
UID:TALK16467@talks.cam.ac.uk
CONTACT:Martin C. Smith
DESCRIPTION:It is possible to reliably identify white dwarfs (WDs) without
  recourse to spectra\, instead using photometric and astrometric measureme
 nts to distinguish them from Main Sequence stars and quasars. WDs' colours
  can also be used to infer their intrinsic properties (effective temperatu
 re\, surface gravity\, etc.)\, but the results obtained must be interprete
 d with care. The difficulties stem from the existence of a solid angle deg
 eneracy\, as revealed by a full exploration of the likelihood\, although t
 his can be masked if a simple best-fit approach is used. Conversely\, this
  degeneracy can be broken if a Bayesian approach is adopted\, as it is the
 n possible to utilise the prior information on the surface gravities of WD
 s implied by spectroscopic fitting. The benefits of such an approach are p
 articularly strong when applied to outliers\, such as the candidate halo a
 nd ultra-cool WDs identified by Vidrih et al. (2007). A reanalysis of thes
 e samples confirms their results for the latter sample but suggests that t
 hat most of the halo candidates are disk WDs in the tails of the photometr
 ic noise distribution.\nSee arXiv:0810.5123
LOCATION:HCR\, IoA
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