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A Long, Hard Look at the Low-Hard State in Accreting Black Holes

J. M. Miller·J. Homan·D. Steeghs·M. Rupen·R. W. Hunstead·R. Wijnands·P. A. Charles·A. C. Fabian
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Abstract

We present the first results of coordinated multi-wavelength observations of the Galactic black hole GX 339-4 in a canonical low-hard state, obtained during its 2004 outburst. XMM-Newton observed the source for 2 revolutions, or approximately 280 ksec; RXTE monitored the source throughout this long stare. The resulting data offer the best view yet obtained of the inner accretion flow geometry in the low-hard state, which is thought to be analogous to the geometry in low-luminosity active galactic nuclei. The XMM-Newton spectra clearly reveal the presence of a cool accretion disk component, and a relativistic Fe K emission line. The results of fits made to both components strongly suggest that a standard thin disk remains at or near to the innermost stable circular orbit, at least in bright phases of the low-hard state. These findings indicate that potential links between the inner disk radius and the onset of a steady compact jet, and the paradigm of a radially-recessed disk in the low-hard state, do not hold universally. The results of our observations can best be explained if a standard thin accretion disk fuels a corona which is closely related to, or consistent with, the base of a compact jet. In a brief examination of archival data, we show that Cygnus X-1 supports this picture of the low/hard state. We discuss our results within the context of disk-jet connections and prevailing models for accretion onto black holes.

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J. M. Miller, J. Homan, D. Steeghs, M. Rupen, R. W. Hunstead, R. Wijnands, P. A. Charles, A. C. Fabian. 2006-08-25. A Long, Hard Look at the Low-Hard State in Accreting Black Holes. https://doi.org/10.1086/508644

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