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High-mass X-ray binary systems are powered by the stellar wind of their donor stars. The X-ray state of Cygnus X-1 is correlated with the properties of the wind which defines the environment of mass accretion. Chandra-HETGS observations close to orbital phase 0 allow for an analysis of the photoionzed stellar wind at high resolution, but because of the strong variability due to soft X-ray absorption dips, simultaneous multi-satellite observations are required to track and understand the continuum, too. Besides an earlier joint Chandra and RXTE observation, we present first results from a recent campaign which represents the best broad-band spectrum of Cyg X-1 ever achieved: On 2008 April 18/19 we observed this source with XMM-Newton, Chandra, Suzaku, RXTE, INTEGRAL, Swift, and AGILE in X- and gamma-rays, as well as with VLA in the radio. After superior conjunction of the black hole, we detect soft X-ray absorption dips likely due to clumps in the focused wind covering >95 % of the X-ray source, with column densities likely to be of several 10^23 cm^-2, which also affect photon energies above 20 keV via Compton scattering.
We have analyzed a Chandra HETGS spectrum of the Galactic black hole Cygnus X-1, obtained at a source flux which is approximately twice that commonly observed in its persistent low-intensity, spectrally-hard state. We find a myriad of absorption line
We improve the method proposed by Yao emph{et al} (2003) to resolve the X-ray dust scattering halos of point sources. Using this method we re-analyze the Cygnus X-1 data observed with {it Chandra} (ObsID 1511) and derive the halo radial profile in di
Context: Cygnus X-1 is a black hole X-ray binary system in which the black hole captures and accretes gas from the strong stellar wind emitted by its supergiant O9.7 companion star. The irradiation of the supergiant star essentially determines the fl
We present X-ray spectral analyses of low mass X-ray binary Cir X-1 during X-ray dips, using the Rossi X-ray Timing Explorer (RXTE) data. Each dip was divided into several segments, and the spectrum of each segment was fitted with a three-component b
We present an analysis of three Chandra High Energy Transmission Gratings observations of the black hole binary Cyg X-1/HDE 226868 at different orbital phases. The stellar wind that is powering the accretion in this system is characterized by tempera