Analysis of hydrogen-rich magnetic white dwarfs detected in the Sloan Digital Sky Survey
Külebi, B., Jordan, S. (Stefan), Euchner, F., Gaensicke, B. T. (Boris T.) and Hirsch, H. (Heiko). (2009) Analysis of hydrogen-rich magnetic white dwarfs detected in the Sloan Digital Sky Survey. Astronomy & Astrophysics, Vol.506 (No.3). pp. 1341-1350. ISSN 0004-6361
WRAP_Gaensicke_14_analysis_hydrogen_rich_aa12570-09.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Official URL: http://dx.doi.org/10.1051/0004-6361/200912570
Context. A large number of magnetic white dwarfs discovered in the SDSS have so far only been analyzed by visual comparison of the observations with relatively simple models of the radiation transport in a magnetised stellar atmosphere.
Aims. We model the structure of the surface magnetic fields of the hydrogen-rich white dwarfs in the SDSS.
Methods. We calculated a grid of state-of-the-art theoretical optical spectra of hydrogen-rich magnetic white dwarfs (WDs) with magnetic field strengths of between 1 MG and 1200 MG for different angles between the magnetic field vector and the line of sight,and for effective temperatures between 7000 K and 50 000 K. We used a least squares minimization scheme with an evolutionary algorithm to find the best-fit magnetic field geometry of the observed data. We used centered dipoles or dipoles that had been shifted
along the dipole axis to model the coadded SDSS fiber spectrum of each object.
Results. We analyzed the spectra of all known magnetic hydrogen-rich (DA) WDs from the SDSS (97 previously published, plus 44 newly discovered) and also investigated the statistical properties of the magnetic field geometries of this sample.
Conclusions. The total number of known magnetic white dwarfs has already been more than tripled by the SDSS and more objects are expected after more systematic searches. The magnetic fields have strengths of between ≈1 and 900 MG. Our results further support the claims that Ap/Bp population is insufficient in generating the numbers and field strength distributions of the observed MWDs, and
that of either another source of progenitor types or binary evolution is needed. Clear indications of non-centered dipoles exist in about ∼50%, of the objects which is consistent with the magnetic field distribution observed in Ap/Bp stars.
|Item Type:||Journal Article|
|Subjects:||Q Science > QB Astronomy|
|Divisions:||Faculty of Science > Physics|
|Library of Congress Subject Headings (LCSH):||White dwarf stars, Magnetic stars, Stars -- Magnetic fields, Magnetic dipoles|
|Journal or Publication Title:||Astronomy & Astrophysics|
|Official Date:||November 2009|
|Page Range:||pp. 1341-1350|
|Access rights to Published version:||Open Access|
|Funder:||Deutsche Forschungsanstalt für Luft- und Raumfahrt (DLR), Alfred P. Sloan Foundation, United States. National Aeronautics and Space Administration (NASA), National Science Foundation (U.S.) (NSF), United States. Dept. of Energy, Japan. Monbushō, Max-Planck-Gesellschaft zur Förderung der Wissenschaften [Max Planck Society for the Advancement of Science], University of Chicago, Fermi National Accelerator Laboratory (Fermilab), Institute for Advanced Study (Princeton, N.J.), Johns Hopkins University, Max-Planck-Institut für Astronomie, New Mexico State University, Princeton University, United States Naval Observatory, University of Washington, International Max Planck Research School for Astronomy and Cosmic Physics (IMPRS), Universität Heidelberg. Heidelberg Graduate School of Fundamental Physics (HGSFP)|
|Grant number:||50 OR 0201 (DLR)|
Aurière, M., Wade, G. A., Silvester, J., et al. 2007, A&A, 475, 1053
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