Discovery of a highly magnetic white dwarf with strong carbon features

Systematic follow-up of high proper-motion stars has identified a new cool magnetic white dwarf that displays a series of spectacular absorption bands in the range 4200-6500 Angstrom. The spectrum bears a striking resemblance to that of LP 790-29, a magnetic DQ star dominated by what are apparently Zeeman-shifted Swan bands of Ct. However, key differences in the detailed s pectra, polarization, and temperature of the two stars indicate that instea d LHS 2229 may represent the first case of a magnetic "peculiar" DQ white d warf, where absorption in the optical is produced by C2H or another carbon- hydrogen compound. Crude arguments suggest that the field strength on LHS 2 229 is in the neighborhood of 10(8) G. BVI photometry proves to be effectiv e in identifying such peculiar stars, since they lie well outside the main white dwarf sequence in a color-color diagram.