New insight into the magnetism of degenerate stars from the analysis of a volume limited sample of white dwarfs

Understand

Many stars evolve into magnetic white dwarfs, and observations may help to understand when the magnetic field appears at the stellar surface, if and how it evolves during the cooling phase, and what are the mechanisms that generate it.

• After obtaining new spectropolarimetric observations and combining them with previous literature data, we have checked the population of about 152 white dwarfs within 20 pc from the Sun for the presence of magnetic fields, with a sensitivity that ranges from better than 1 kG for most of the stars of spectral class DA, to 1 MG for some of the featureless white dwarfs.
• We find that 33 white dwarfs of the local 20 pc volume are magnetic.
• Statistically the data are consistent with the possibility that the frequency of the magnetic field occurrence is similar in stars of all spectral classes, except that in the local 20 pc volume, either DQ stars are more frequently magnetic, or host much stronger fields than average.