Surveying DC white dwarfs for magnetic fields

A survey of 52 DC white dwarf stars was conducted in circular spectropolarimetry to search for magnetic fields greater than or similar to 30 kG. Four DC stars were discovered with magnetic fields above 30 kG: G111-49 with B-e similar to -220 MG, G183-35 with B-e = +6.8 +/- 0.5 MG, G256-7 with B-e = + 4.9 +/- 0.5 MG, and G234-4 with B-e = +39.6 +/- 11.6 kG. A new magnetic DE) white dwarf was also discovered, LB 8827 with B-e = 1.0 +/- 0.5 MG. A total of 15% of the white dwarfs in the survey have a magnetic field >30 kG. This value is far larger than the 2% of DA stars, but more than half of the DC stars were originally misclassified. Only 5% of the reclassified DC stars have magnetic fields above 30 kG. Non-white dwarfs were also observed: the two BL Lacs are unpolarized in circular polarization and an extreme carbon star was discovered. Three magnetic stars from the DC white dwarf survey were reobserved to investigate the possibility of rotation. Two are definitely rotating: LHS 1734 with 16 minutes less than or similar to P < 1 yr and Gl58-45 (=LHS 1044) with a probable period P similar to 11 hr but a definite period P less than or equal to 1 day or P similar to a few days. G183-35 might be rotating with 50 minutes less than or similar to P < a few yr.