König, M., Beuermann, K. (Klaus) and Gänsicke, B. T. (Boris T.). (2006) Irradiated atmospheres of accreting magnetic white dwarfs with an application to the polar AM Herculis. Astronomy & Astrophysics, Vol.449 (No.3). pp. 1129-1137. ISSN 0004-6361

PDF WRAP_Gansicke_82_Irradiated_atmospheres.pdf - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader Download (347Kb)

Abstract

We present a pilot study of atmospheres of accreting magnetic white dwarfs irradiated by intense fluxes at ultraviolet to infrared wavelengths. The model uses a standard LTE stellar atmosphere code which is expanded by introducing an angle-dependent external radiation source. The present results are obtained for an external source with the spectral shape of a 10 000 K blackbody and a freely adjustable spectral flux. The model provides an explanation for the observed largely filled-up Lyman lines in the prototype polar AM Herculis during its high states. It also confirms the hypotheses (i) that irradiation by cyclotron radiation and other radiation sources is the principle cause for the large heated polar caps surrounding the accretion spots on white dwarfs in polars and (ii) that much of the reprocessed light appears in the far ultraviolet and not in the soft X-ray regime as suggested in the original simple theories. We also briefly discuss the role played by hard X-rays in heating the polar cap.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Stars -- Atmospheres, White dwarf stars, Magnetic stars, Accretion (Astrophysics), Cataclysmic variable stars
Journal or Publication Title:	Astronomy & Astrophysics
Publisher:	EDP Sciences
ISSN:	0004-6361
Date:	April 2006
Volume:	Vol.449
Number:	No.3
Page Range:	pp. 1129-1137
Identification Number:	10.1051/0004-6361:20054336
Status:	Peer Reviewed
Access rights to Published version:	Open Access
Funder:	Deutsche Forschungsgemeinschaft (DFG), Particle Physics and Astronomy Research Council (Great Britain) (PPARC)
References:	Araujo-Betancor, S., Gänsicke, B. T., Long, K., et al. 2005, ApJ, 622, 589 Bailey, J., Hough, J. H., & Wickramasinghe, D. 1988, MNRAS, 233, 395 Barman, T. S., Hauschildt, P. H., & Allard, F. 2004, ApJ, 614, 338 Beuermann, K. 2004, in IAU Coll. 190: Magnetic Cataclysmic Variables, ASP Conf. Ser., 315, 187 Brett, J. M., & Smith, R. C. 1993, MNRAS, 264, 641 Fischer, A., & Beuermann, K. 2001, A&A, 373, 211 Frank, J., King, A. R., & Lasota, J.-P. 1988, A&A, 193, 113 Gänsicke, B. T., Beuermann, K., & de Martino, D. 1995, A&A, 303, 127 Gänsicke, B. T., Hoard, D.W., Beuermann, K., Sion, E. M., & Szkody, P. 1998, A&A, 338, 933 Gänsicke, B. T., Fischer, A., Silvotti, R., & de Martino, D. 2001, A&A, 372, 557 Gänsicke, B. T., Long, K., Barstow, M., & Hubeny, I. 2005, ApJ, in press Greeley, B.W., Blair,W. P., Long, K. S., & Raymond, J. C. 1999, ApJ, 513, 491 Heise, J., & Verbunt, F. 1988, A&A, 189, 112 King, A. R., & Lasota, J. P. 1979, MNRAS, 188, 653 König, M. 2005, Ph.D. Thesis, University of Göttingen, Germany Kuijpers, J., & Pringle, J. E. 1982, A&A, 114, L4 Lamb, D. Q., & Masters, A. R. 1979, ApJ, 234, L117 London, R., McCray, R., & Auer, L. H. 1981, ApJ, 243, 970 Mauche, C. W., & Raymond, J. C. 1998, ApJ, 505, 869 Priedhorsky, W., Matthews, K., Neugebauer, G., Werner, M., & Krzeminski, W. 1978, ApJ, 226, 397 Ramsay, G., & Cropper, M. 2004, MNRAS, 347, 497 Rybicki, G. B. 1971, JQRST, 11, 589 Schachter, J., Filippenko, A. V., Kahn, S. M., & Paerels, F. B. S. 1991, ApJ, 373, 633 Thomson, A. M., & Cawthorne, T. V. 1987, MNRAS, 224, 425 Thorstensen, J. 2003, AJ, 126, 3017 Townsley, D. M., & Bildsten, L. 2003, ApJ, 596, L227 van Teeseling, A., Heise, J., & Paerels, F. 1994, A&A, 281, 119 Woelk, U., & Beuermann, K. 1992, A&A, 256, 498
URI:	http://wrap.warwick.ac.uk/id/eprint/3564

Request changes to a record

Actions (login required)

View Item