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Title

The high-energy emission of GRO J1655-40 as revealed with INTEGRAL spectroscopy of the 2005 outburst

AuthorsCaballero-García, María Dolores; Miller, J. M.; Kuulkers, E.; Trigo, M. D.; Homan, J.; Lewin, W. H. G.; Kretschmar, P.; Domingo-Garau, Albert ; Mas-Hesse, J. Miguel ; Wijnands, R.; Fabian, A. C.; Fender, R. P.; Klis, M. van der
KeywordsAccretion and accretion disks
Binaries: general
Black hole physics
Gamma rays: observations
Radiation mechanisms: non-thermal
Radiation mechanisms: thermal
Issue Date1-Nov-2007
PublisherAmerican Astronomical Society
Institute of Physics Publishing
CitationAstrophysical Journal 669(1): 534-545 (2007)
AbstractWe present broadband (3-500 keV) INTEGRAL X-ray spectra and X-ray/optical light curves of the luminous black hole X-ray transient and relativistic jet source GRO J1655-40. Our analysis covers four Target of Opportunity observations of the outburst that started in 2005 February. We find that the high-energy emission of GRO J1655-40 can be modeled well with an unbroken power law (with photon indices Γ of 1.72 ± 0.03 and 2.21 ± 0.04 for the first and second observations). These correspond to hard and thermal-dominant states, respectively. In contrast to many other black hole spectra, high-energy complexity in the form of a break or cutoff is not required for the hard state, contrary to previous expectations. We show for the first time that Comptonization by nonthermal electrons is the dominant process behind the high-energy emission in the hard state. We discuss our results in terms of models for broadband emission and accretion flows in stellar-mass black holes.
Description12 pages, 10 figures, 3 tables.-- ISI Article Identifier: 000250480600041.-- ArXiv pre-print available at: http://arxiv.org/abs/0706.1302
Publisher version (URL)http://dx.doi.org/10.1086/520764
URIhttp://hdl.handle.net/10261/13063
DOI10.1086/520764
ISSN0004-637X
Appears in Collections:(CAB) Artículos
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