Journal Article

Evidence for a change in the X-ray radiation mechanism in the hard state of Galactic black holes

M. A. Sobolewska, I. E. Papadakis, C. Done and J. Malzac

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 417, issue 1, pages 280-288
Published in print October 2011 | ISSN: 0035-8711
Published online October 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19209.x
Evidence for a change in the X-ray radiation mechanism in the hard state of Galactic black holes

More Like This

Show all results sharing this subject:

  • Astronomy and Astrophysics

GO

Show Summary Details

Preview

We present results on the spectral variability of two Galactic black hole X-ray binaries, GRO J1655–40 and GX 339–4, in the hard state. We confirm a transition in behaviour of the photon index with luminosity, such that the well-known decrease in X-ray photon index with decreasing luminosity only continues down to Lbol∼ 0.01LE. Below this point, the photon index increases again. For Comptonization models, this implies that the ratio of the Compton luminosity to seed photon luminosity, ℓh/ℓs, changes with bolometric luminosity, consistent with a scenario where seed photons change from cyclo-synchrotron at the lowest luminosities to those from a truncated disc. Alternatively, the transition could mark the point below which the non-thermal jet starts to dominate, or where reprocessed photons replace the viscous photons in an outflowing corona model.

Keywords: accretion, accretion discs; black hole physics; X-rays: binaries

Journal Article.  7354 words.  Illustrated.

Subjects: Astronomy and Astrophysics

Full text: subscription required

How to subscribe Recommend to my Librarian

Users without a subscription are not able to see the full content. Please, subscribe or login to access all content.