Discovery of kilogauss magnetic fields on the nearby white dwarfs WD 1105–340 and WD 2150+591⋆
Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, UK
e-mail: John.Landstreet@Armagh.ac.uk, Stefano.Bagnulo@Armagh.ac.uk
2 University of Western Ontario, Department of Physics & Astronomy, London, Ontario N6G 1P7, Canada
Accepted: 24 January 2019
Magnetic fields are present in roughly 10% of white dwarfs. These fields affect the structure and evolution of such stars, and may provide clues about their earlier evolution history. Particularly important for statistical studies is the collection of high-precision spectropolarimetric observations of (1) complete magnitude-limited samples and (2) complete volume-limited samples of white dwarfs. In the course of one of our surveys we have discovered previously unknown kG-level magnetic fields on two nearby white dwarfs, WD 1105–340 and WD 2150+591. Both stars are brighter than mV = 15. WD 2150+591 is within the 20 pc volume around the Sun, while WD 1105–340 is just beyond 25 pc in distance. These discoveries increase the small sample of such weak-field white dwarfs from 21 to 23 stars. Our data appear consistent with roughly dipolar field topology, but it also appears that the surface field structure may be more complex on the older star than on the younger one, a result similar to one found earlier in our study of the weak-field stars WD 2034+372 and WD 2359–434. This encourages further efforts to uncover a clear link between magnetic morphology and stellar evolution.
Key words: stars: magnetic field / white dwarfs / polarization / stars: individual: WD 1105–340 / stars: individual: WD 2150+591
Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii, under Programme 18AC006; on observations made with ESO Telescopes at the La Silla Paranal Observatory, under programme IDs 0101.D-0103 and 0102.D-0045(A),; and at the Observatorios de Canarias del IAC with the William Herschel Telescope, operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Observatorio del Roque de los Muchachos, under Programme 18B-P15.
© ESO 2019