Kilo-Gauss Magnetic Fields in Three DA White Dwarfs

Abstract

We have detected longitudinal magnetic fields between 2 and 4 kG in three normal DA white dwarfs (WD0446¡790, WD1105¡048, WD2359¡434) out of a sample of 12 by using optical spectropolarimetry done with the VLT Antu 8 m telescope equipped with FORS1. With the exception of 40 Eri B (4 kG) these are the first positive detections of magnetic fields in white dwarfs below 30 kG. A detection rate of 25 % (3/12) may indicate now for the first time that a substantial fraction of white dwarfs have weak magnetic fields. This result, if confirmed by future observations, would form a cornerstone for our understanding of the evolution of stellar magnetic fields.