Possible Detection of Weak Magnetic Fields in Two White Dwarfs, Including the Pulsating WD 1647+591

摘要

We present new results of a survey for weak magnetic fields among DA white dwarfs. We have detected variable circular polarization in the Ha line of the pre-white dwarf star WD 1036+433 (DAO/sdO) and suspect the presence of a kG longitudinal magnetic field in the pulsating white dwarfs WD 1647+591. From our data we estimate that the longitudinal magnetic field of WD 1036+433 varies from —1.1 ± 3.2 kG to +9.6+2.6 kG with a period longer than 2 h, with a mean of about +5 kG, and that the field of the pulsating white dwarf WD 1647+591 varies from —0.5 ± 2.8 kG to —8.7 ± 3.2 kG, with a mean of —3.8 + 1.7 kG. These results, if confirmed by future observations, provide theories of stellar magnetism with important new results.