A new soft X-ray spectral model for polars with an application to AM Herculis

K. Beuermann; V. Burwitz; K. Reinsch

doi:doi:10.1051/0004-6361/201219217

Issue		A&A Volume 543, July 2012


Article Number		A41
Number of page(s)		5
Section		Stellar structure and evolution
DOI		http://dx.doi.org/10.1051/0004-6361/201219217
Published online		25 June 2012

A&A 543, A41 (2012)

A new soft X-ray spectral model for polars with an application to AM Herculis^⋆

K. Beuermann¹, V. Burwitz² and K. Reinsch¹

¹ Institut für Astrophysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
e-mail: beuermann@astro.physik.uni-goettingen.de
² Max-Planck-Institut für Extraterrestrische Physik, 85740 Garching b. München, Germany

Received: 13 March 2012
Accepted: 1 May 2012

Abstract

We present a simple heuristic model for the time-averaged soft X-ray temperature distribution in the accretion spot on the white dwarf in polars. The model is based on the analysis of the Chandra LETG spectrum of the prototype polar AM Her and involves an exponential distribution of the emitting area vs. blackbody temperature a(T) = a₀ exp( − T/T₀). With one free parameter besides the normalization, it is mathematically as simple as the single blackbody, but is physically more plausible and fits the soft X-ray and far-ultraviolet spectral fluxes much better. The model yields more reliable values of the wavelength-integrated flux of the soft X-ray component and the implied accretion rate than reported previously.

Key words: accretion, accretion disks / novae, cataclysmic variables / stars: individual: AM Her / X-rays: binaries

^⋆

Based on observations with the Chandra and ROSAT satellites.

© ESO, 2012

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

A new soft X-ray spectral model for polars with an application to AM Herculis⋆

A new soft X-ray spectral model for polars with an application to AM Herculis^⋆