DISCOVERY OF A MAGNETIC NONMAGNETIC DOUBLE-DEGENERATE BINARY-SYSTEM

We report the discovery of an unresolved binary system consisting of t wo degenerate stars: one a polarized object with an inferred magnetic field among the largest yet found on a white dwarf; the other a normal DA with no detectable field. We have deconvolved the composite 1250 a ngstrom-2.2 mum energy distribution into individual spectra and find t hat, with the exception of the graphic difference in magnetic field st rength, the two stars are remarkably similar. For the normal DA, T(eff ) almost-equal-to 14,500 K, log g almost-equal-to 8.5, and M = 0.91 +/ - 0.07 M., while the magnetic component has T(eff) almost-equal-to 16, 000 K, log g almost-equal-to 8.5, and 0.76 less-than-or-equal-to M/M. < 1.00. The parameters of the latter are less accurately determined si nce it appears to have an atmosphere dominated by an element other tha n hydrogen. At a distance of about 40 pc, the projected separation of the stellar components could be as large as 20 AU. The binary might th erefore be a wide pair in which two stars of similar initial mass evol ved into two very different end states. On the other hand, it could be an unusual product of close binary evolution, in which case this woul d be the first such example whose combined mass appears to exceed the Chandrasekhar limit. Potential implications and future observations to clarify the evolutionary and magnetic status of the system are sugges ted.