The low-mass white dwarf companion to beta Crateris

We present FUSE H Lyman series spectroscopy of the hot white dwarf companion to the 4th magnitude A1=III star Beta-Crt, which shows that it has an unusually low mass, M(WD) = 0:43 M(Sun) and has almost certainly evolved through binary interaction. This system could be a longsought remnant of Algol-type evolution, although radial velocity measurements appear to show that the pair are not close. Instead, micro-variations in the proper motion of Beta-Crt as measured by Hipparcos suggest that the period could be as high as ,10 yr. However, a lowmass white dwarf in a system with a period >=3 yr is difficult to explain by conventional models for binary evolution. We speculate on alternative models for the evolution of this system which involve an eccentric binary or multiple components.