Euchner, F., Jordan, S., Beuermann, K., Reinsch, K. and Gänsicke, B. T. (Boris T.). (2006) Zeeman tomography of magnetic white dwarfs - III. The 70-80 Megagauss magnetic field of PG1015+014. Astronomy & Astrophysics, Vol.451 (No.2). pp. 671-681. ISSN 0004-6361

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Abstract

Aims. We analyse the magnetic field geometry of the magnetic DA white dwarf PG1015+014 with our Zeeman tomography method. Methods. This study is based on rotation-phase resolved optical flux and circular polarization spectra of PG1015+014 obtained with FORS1 at the ESO VLT. Our tomographic code makes use of an extensive database of pre-computed Zeeman spectra. The general approach has been described in Papers I and II of this series. Results. The surface field strength distributions for all rotational phases of PG1015+014 are characterised by a strong peak at 70 MG. A separate peak at 80MG is seen for about one third of the rotation cycle. Significant contributions to the Zeeman features arise from regions with field strengths between 50 and 90 MG. We obtain equally good simultaneous fits to the observations, collected in five phase bins, for two different field parametrizations: (i) a superposition of individually tilted and off-centred zonal multipole components; and (ii) a truncated multipole expansion up to degree l = 4 including all zonal and tesseral components. The magnetic fields generated by both parametrizations exhibit a similar global structure of the absolute surface field values, but differ considerably in the topology of the field lines. An effective photospheric temperature of T-eff = 10 000 +/- 1000 K was found. Conclusions. Remaining discrepancies between the observations and our best-fit models suggest that additional small-scale structure of the magnetic field exists which our field models are unable to cover due to the restricted number of free parameters.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	May 2006
Volume:	Vol.451
Number:	No.2
Number of Pages:	11
Page Range:	pp. 671-681
Identification Number:	10.1051/0004-6361:20064840
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access
Funder:	Federal Ministry for Education and Research/German Aerospace Center (BMBF/DLR) (Germany)
Grant number:	50 OR 9903 6. B.T.G.
URI:	http://wrap.warwick.ac.uk/id/eprint/33619

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