Helium-Core White Dwarfs in Globular Clusters
  We examine the theoretical implications of a population of low-mass helium-core white dwarfs in globular clusters. In particular, we focus on the observed population in the core of NGC 6397, where several low-mass white dwarf canditates have been identified as ``non-flickerers'' by Cool and collaborators. Age and mass estimates from cooling models, combined with dynamical and evolutionary considerations, lead us to infer that the dark binary companions are C/O white dwarfs rather than neutron stars. Furthermore, we find that the progenitor binaries very likely underwent an exchange interaction within the last 1.e9 years. We examine the prospects for detecting a similar population in other globular clusters, with particular attention to the case of 47 Tuc. 
Brad Hansen (UCLA), Vassiliki Kalogera (Northwestern), Frederic A.   Rasio (Northwestern)