Discovery of kilogauss magnetic fields in three DA white dwarfs
Abstract
We have detected longitudinal magnetic fields between 2 and 4 kG in three (WD 0446-790, WD 1105-048, WD 2359-434) out of a sample of 12 normal DA white dwarfs 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. Although suspected, it was not clear whether a significant fraction of white dwarfs contain magnetic fields at this level. These fields may be explained as relics from magnetic fields in the main-sequence progenitors considerably enhanced by magnetic flux conservation during the shrinkage of the core. A detection rate of 25% (3/12) may indicate now for the first time that a substantial fraction of white dwarfs have a weak magnetic field. This result, if confirmed by future observations, would form a cornerstone for our understanding of the evolution of stellar magnetic fields.
Based on observations collected at the European Southern Observatory, Paranal, Chile, under programme ID 70.D-0259.- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2004
- DOI:
- 10.1051/0004-6361:20040355
- arXiv:
- arXiv:astro-ph/0405308
- Bibcode:
- 2004A&A...423.1081A
- Keywords:
-
- stars: magnetic fields;
- stars: individual: WD0446-790;
- WD1105-048;
- WD2359-434;
- Astrophysics
- E-Print:
- 15 pages, 7 figures, Astronomy and Astrophysics, in press