Volume 423, Number 3, September I 2004
|Page(s)||1081 - 1094|
|Section||Stellar structure and evolution|
|Published online||12 August 2004|
Discovery of kilogauss magnetic fields in three DA white dwarfs*
Max-Planck-Institut für Aeronomie, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany e-mail: email@example.com
2 Institut für Astronomie und Astrophysik, Eberhard-Karls-Universität Tübingen, Sand 1, 72076 Tübingen, Germany
3 Astronomisches Rechen-Institut, Mönchhofstr. 12–14, 69120 Heidelberg, Germany
4 Department of Physics & Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
5 Institut für Astronomie, ETH Zentrum, 8092 Zürich, Switzerland
6 European Southern Observatory, Casilla 19001, Santiago 19, Chile
Accepted: 12 May 2004
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.
Key words: stars: magnetic fields / stars: individual: WD0446-790, WD1105-048, WD2359-434
© ESO, 2004
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