Discovery of a dwarf carbon star with a white dwarf companion and of a highly magnetic degenerate star

We report herein the discovery of two very unusual stars, identified during follow-up spectroscopy of candidates from the Second Byurakan Survey (SBS). SBS 1517-1-5017 is an object with a composite spectrum which we identify as a dwarf carbon star plus white dwarf binary - only the second such combination known. Since the system is unresolved spatially, we cannot yet determine whether the separation is small enough for mass transfer to have occurred when the evolved component was an asymptotic giant. The second unusual object we examine is SBS 1349 + 5434, which we show to be a magnetic white dwarf with an equivalent polar field strength among the strongest found among white dwarfs at 760 × 10⁶ G. Given its immense field, the low measured polarization - both linear and circular - of this object is surprising and suggests that the field pattern over the stellar surface may be quite complex.