The low-mass white dwarf companion to beta Crateris

We present FUSE H Lyman series spectroscopy of the hot white dwarf companio n to the 4th magnitude A1 III star beta Crt, which shows that it has an unu sually low mass, M-WD = 0.43 M-circle dot, and has almost certainly evolved through binary interaction. This system could be a long-sought 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 h igh as similar to 10 yr. However, a low-mass white dwarf in a system with a period greater than or similar to3 yr is difficult to explain by conventio nal models for binary evolution. We speculate on alternative models for the evolution of this system which involve an eccentric binary or multiple com ponents.