INTEGRAL-RXTE observations of Cygnus X-1
Nowak, M. A.; Rodriguez, J.; Wilms, J.; Schönfelder, V.; Pottschmidt, K.; Kretschmar, P.; Pooley, G. G.; Staubert, R.; Courvoisier, T. J. -L.; Zdziarski, A. A.; Beckmann, V.; Chernyakova, M.; Martínez-Núñez, S.; Gleissner, T.
Germany, Switzerland, Russia, United States, France, Poland, United Kingdom, Spain, Denmark
Abstract
We present first results from contemporaneous observations of Cygnus X-1 with INTEGRAL and RXTE, made during INTEGRAL's performance verification phase in 2002 November and December. Consistent with earlier results, the 3-250 keV data are well described by Comptonization spectra from a Compton corona with a temperature of kT ~ 50-90 keV and an optical depth of tau ~ 1.0-1.3 plus reflection from a cold or mildly ionized slab with a covering factor of Omega /2pi ~ 0.2-0.3. A soft excess below 10 keV, interpreted as emission from the accretion disk, is seen to decrease during the 1.5 months spanned by our observations. Our results indicate a remarkable consistency among the independently calibrated detectors, with the remaining issues being mainly related to the flux calibration of INTEGRAL.
Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA.