The truncated and evolving inner accretion disc of the black hole GX 339-4
Journal
Date Issued
2015
Author(s)
Description
The authors are very grateful to Javier Garcia for the use of the reflection model xillver , and Stefano Bianchi for useful discussion. We also thank the referee for careful and constructive comments that have undoubtedly improved this article. This research has made use of the General High-energy Aperiodic Timing Software (GHATS) package developed by T. M. Belloni at INAF – Observatorio Astronomico di Brera. It has also made use of data obtained with the XMM-Newton , Suzaku , and RXTE satellites. D.S.P. acknowledges financial support from the STFC. G.P. acknowledges support via an EU Marie Curie Intra-European fellowship under contract No. FP-PEOPLE-2012-IEF-331095. T.M.D. acknowledges funding via an EU Marie Curie Intra-European Fellowship under contract No. 2011-301355.
Abstract
The nature of accretion onto stellar mass black holes in the low/hard state remains unresolved, with some evidence suggesting that the inner accretion disc is truncated and replaced by a hot flow. However, the detection of relativistic broadened Fe emission lines, even at relatively low luminosities, seems to require an accretion disc extending fully to its innermost stable circular orbit. Modelling such features is, however, highly susceptible to degeneracies, which could easily bias any interpretation. We present the first systematic study of the Fe line region to track how the inner accretion disc evolves in the low/hard state of the black hole GX 339-4. Our four observations display increased broadening of the Fe line over two magnitudes in luminosity, which we use to track any variation of the disc inner radius. We find that the disc extends closer to the black hole at higher luminosities, but is consistent with being truncated throughout the entire low/hard state, a result which renders black hole spin estimates inaccurate at these stages of the outburst. Furthermore, we show that the evolution of our spectral inner disc radius estimates corresponds very closely to the trend of the break frequency in Fourier power spectra, supporting the interpretation of a truncated and evolving disc in the hard state.
Volume
573
Start page
A120
Issn Identifier
0004-6361
Ads BibCode
2015A&A...573A.120P
Rights
open.access
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