Probing Strong Gravity near Black Holes

Prague, Czech Republic
2010 February 15–18

Broadband properties of Cygnus X-1 and comparisons with several microquasars

M. Cadolle-Bel, D.M. Marcu, V. Grinberg, K. Pottschmidt, J. Wilms, A.M. Lohfink, F. Fuerst, M. Hanke, M.A. Nowak, S. Markoff, S. Corbel, J.A. Tomsick, J. Rodriguez, G.G. Pooley, M. Ribo, D. Hannikainen, P. D'avanzo, J. Malzac, on behalf of a larger collaboration

In the light of recent observations obtained with XMM-Newton, INTEGRAL, RXTE, Swift, MAGIC and ground-based instruments, we will present some progress that has been made in the understanding of extreme gravity phenomena around stellar-mass BHs. Focusing on Cygnus X-1, we will show an analysis of extensive recent monitoring obtained as part of the 2007 to 2009 Cygnus Region Key Program observations of the INTEGRAL mission. Cygnus X-1 underwent several bright flares seen by INTEGRAL, from 2006 until recently (mid-2009), sometimes accompanied by flares seen at TeV (MAGIC) and in the optical range. We will then concentrate on constraining the spectral parameters of the hard spectrum, which is crucial so as to understand the physics of the hot plasma (jet base and/or corona). We will also compare radio to X-ray broad band spectra of two emission states (hard and soft) of Cygnus X-1 to the results of multiwavelength campaigns on XTE J1818-245, XTE J1817-330 and H 1743-322. Imaging, continuum spectroscopy and timing will be shown and discussed, in the context of high-energy phenomena and future perspectives of probing gravity around microquasars.