High Energy Astrophysics Division Meeting 2010

Big Island, Hawaii
2010 March 1–4

Corona, Jet, and Relativistic Line Models for Suzaku/RXTE/Chandra-HETG Observations of the Cygnus X-1 Hard State

Michael A. Nowak, Manfred Hanke, Sarah N. Trowbridge, Sera B. Markoff, Jörn Wilms, Katja Pottschmidt, Paolo Coppi, Dipankar Maitra, John E. Davis

We conducted a series of four simultaneous Suzaku-RXTE observations of the galactic black hole Cyg X-1 in what were historically low flux and hard spectral states. The last of these observations (April 2008) was also simultaneous with every X-ray and gamma-ray satellite flying at that time, including Chandra-HETG. The HETG spectra are crucial for modeling the ionized absorbtion from the "focused-wind" of the secondary, which is present and must be accounted for in all of our spectra. Our data give an unprecedented view of the 0.8–300 keV spectra of Cyg X-1, and hence bear upon both corona and X-ray emitting jet models of black hole hard states. Three models fit the spectra well: coronae with thermal or mixed thermal/non-thermal electron populations, and jets. All three agree that the known spectral break at 10 keV is not solely due to the presence of reflection, but give different underlying explanations for the augmentation of this break. Thus whereas all three models agree that there must be a relativistically broadened Fe line, the strength and inner radius of such a line is dependent upon the specific model. We look at the relativistic line in detail, accounting for the narrow Fe emission and ionized absorption detected by HETG. Although the specific relativistic parameters of the line are continuum-dependent, none of these models allow for an inner disk radius that extends to radii greater than 40 GM/c2.


Cygnus X-1: shedding light on the spectral variability of the hard state of black holes

K. Pottschmidt, D.M. Marcu, V. Grinberg, J. Wilms, M. Cadolle-Bel, A.M. Lohfink, F. Fuerst, M. Hanke, M.A. Nowak, S.B. Markoff, J.A. Tomsick, J. Rodriguez, G.G. Pooley

We present an analysis of extensive recent monitoring observations of the black hole X-ray binary Cygnus X-1 obtained as part of the 2007 to 2009 Cygnus Region Key Program observations of the INTEGRAL mission. Cygnus X-1 is one of only three persistent black hole binaries that spend most of their time in the hard spectral state (see also contribution by A.M. Lohfink on INTEGRAL monitoring of GRS 1758-258). We concentrate on constraining the parameter range of the hard spectrum, a measurement that is typically difficult to obtain with high accuracy for transient sources, but which is important to know in order to understand the physics of the hot plasma of the jet base and/or the corona. While the hard X-ray spectrum of Cyg X-1 is one of the best studied examples of its kind, e.g., through our years long monitoring campaign with RXTE, the INTEGRAL monitoring allows us to study the spectral evolution from about half an hour over a few days to a few weeks, timescales that have been only sparsely sampled so far. After spending ~3 years in the hardest regime of its parameter space (see also contribution by M.A. Nowak on multi-satellite hard state observations of Cyg X-1), the source displayed a softening and flaring episode in-mid 2009. We compare radio to X-ray broad band spectra (AMI, RXTE, INTEGRAL) of these two emission states.