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Irradiated atmospheres of accreting magnetic white dwarfs with an application to the polar AM Herculis

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König, M., Beuermann, K. (Klaus) and Gaensicke, 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

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Official URL: http://dx.doi.org/10.1051/0004-6361:20054336

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

Official Date:

3 April 2006

Dates:

Date	Event
11 October 2005	Submitted
12 December 2005	Accepted
3 April 2006	Published

Volume:

Vol.449

Number:

No.3

Page Range:

pp. 1129-1137

Identification Number:

10.1051/0004-6361:20054336

Status:

Peer Reviewed

Publication Status:

Published

Access rights to Published version:

Open Access

Funder:

Deutsche Forschungsgemeinschaft (DFG), Particle Physics and Astronomy Research Council (Great Britain) (PPARC)

References:

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