X-ray spectra from accretion disks illuminated by protons

Free access article

Issue		A&A Volume 387, Number 3, June I 2002


Page(s)		907 - 917
Section		Formation, structure and evolution of stars
DOI		http://dx.doi.org/10.1051/0004-6361:20020293

A&A 387, 907-917 (2002)
DOI: 10.1051/0004-6361:20020293

X-ray spectra from accretion disks illuminated by protons

B. Deufel, C. P. Dullemond and H. C. Spruit

Max-Planck-Institut für Astrophysik, Karl-Schwarzschildstr. 1, 85740 Garching, Germany

(Received 31 August 2001 / Accepted 26 February 2002 )

Abstract
The X-ray spectrum from a cool accretion disk heated by virialized protons is computed. The cool disk is either embedded in a magnetically heated accretion disk corona or partly extends into an ion supported torus (or ADAF). We calculate the stationary equilibrium between proton heating, electron thermal conduction and the radiative losses by bremsstrahlung and Compton scattering. A heated surface layer on top of the accretion disk is produced with temperatures between 60-90 keV above a cool layer with temperatures of 0.01 keV (AGN) and 1 keV (galactic black hole candidates). The spectra produced by the surface layer are reminiscent of hard state spectra, but a bit too steep, especially for AGN's. Near the inner edge of the disk, where the optical depth of the disk $\tau \lesssim 1$ , we find that the cool component of the disk disappears. Instead, the hot protons from the corona/ADAF heat the disk, on a dynamical time-scale, to temperatures of several 100 keV, limited by pair production. This region, here called a "warm disk", could contribute significantly to the hard X-ray spectra and could be important for feeding material into an ADAF.

Key words: accretion, accretion disks -- black hole physics -- X-rays: galaxies -- X-rays: stars

Offprint request: B. Deufel, bed@mpa-garching.mpg.de

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.