EDP Sciences
Free access
Issue
A&A
Volume 463, Number 1, February III 2007
Page(s) 1 - 9
Section Astrophysical processes
DOI http://dx.doi.org/10.1051/0004-6361:20066203


A&A 463, 1-9 (2007)
DOI: 10.1051/0004-6361:20066203

Re-condensation from an ADAF into an inner disk: the intermediate state of black hole accretion?

F. Meyer1, B. F. Liu2, and E. Meyer-Hofmeister1

1  Max-Planck-Institut für Astrophysik, Karl- Schwarzschildstr. 1, 85740 Garching, Germany
    e-mail: [frm;emm]@mpa-garching.mpg.de
2  National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, PO Box 110, Kunming 650011, PR China
    e-mail: bfliu@ynao.ac.cn

(Received 7 August 2006 / Accepted 13 October 2006 )

Abstract
Context.Accretion onto galactic and supermassive black holes occurs in different modes, which are documented in hard and soft spectral states, commonly attributed to an advection-dominated flow (ADAF) inside a truncated disk and standard disk accretion, respectively. At the times of spectral transition an intermediate state is observed, for which the accretion flow pattern is still unclear.
Aims.We analyze the geometry of the accretion flow when the mass flow rate in the disk decreases (soft/hard transition) and evaporation of gas into the coronal flow leads to disk truncation.
Methods.We evaluate the physics of an advection-dominated flow affected by thermal conduction to a cool accretion disk underneath.
Results.We find re-condensation of gas from the ADAF into the underlying inner disk at distances from the black hole and at rates, that depend on the properties of the hot ADAF and vary with the mass accretion rate. This sustains an inner disk for longer than a viscous decay time after the spectral transition occurred, in accordance with the spectra that indicate cool gas in the neighborhood of the accreting black hole. The model allows us to understand why Cyg X-1 does not show hysteresis in the spectral state transition luminosity that is commonly observed for X-ray transient sources.
Conclusions.Our results shed new light on the complex mass flow pattern during spectral state transition.


Key words: accretion, accretion disks -- black hole physics -- X-rays: binaries -- stars: individual: Cyg X-1



© ESO 2007

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.