Details

Autor(en) / Beteiligte

• Hollands, M. A.
• Gänsicke, B. T.
• Koester, D.

Titel

The incidence of magnetic fields in cool DZ white dwarfs

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2015-06, Vol.450 (1), p.681-690

Ort / Verlag

London: Oxford University Press

Erscheinungsjahr

2015

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Little is known about the incidence of magnetic fields among the coolest white dwarfs. Their spectra usually do not exhibit any absorption lines as the bound–bound opacities of hydrogen and helium are vanishingly small. Probing these stars for the presence of magnetic fields is therefore extremely challenging. However, external pollution of a cool white dwarf by, e.g. planetary debris, leads to the appearance of metal lines in its spectral energy distribution. These lines provide a unique tool to identify and measure magnetism in the coolest and oldest white dwarfs in the Galaxy. We report the identification of seven strongly metal polluted, cool (T eff < 8000 K) white dwarfs with magnetic field strengths ranging from 1.9 to 9.6 MG. An analysis of our larger magnitude-limited sample of cool DZ yields a lower limit on the magnetic incidence of 13 ± 4 per cent, noticeably much higher than among hot DA white dwarfs.