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Preprint A/03

INTEGRAL-RXTE observations of Cygnus X-1

K. Pottschmidt (1,2), J. Wilms (3), M. Chernyakova (2,4), M. A. Nowak (5), J. Rodriguez (2,6), A. A. Zdziarski (7), V. Beckmann (2,3), P. Kretschmar (1,2), T. Gleissner (3), G. G. Pooley (8), S. Martínez-Núñez (9,10), T. J.-L. Courvoisier (2,11), V. Schönfelder (1) and R. Staubert (3)

1 Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85748 Garching, Germany
2 INTEGRAL Science Data Centre, Chemin d'Écogia 16, 1290 Versoix, Switzerland
3 Institut für Astronomie und Astrophysik - Abt. Astronomie, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
4 Astro Space Center of the PN Lebedev Physical Institute, 84/32 Profsoyuznaya Street, Moscow 117997, Russia
5 MIT-CXC, NE80-6077, 77 Massachusetts Ave., Cambridge, MA 02139, USA
6 DSM/DAPNIA/Service d'Astrophysique (CNRS FRE 2591), CEA Saclay, 91191 Gif-sur-Yvette, France
7 Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warszawa, Poland
8 Astrophysics, Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, UK
9 GACE, Instituto de Ciencia de los Materiales, Universidad de Valencia, PO Box 22085, 46071 Valencia, Spain
10 Danish Space Research Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø., Denmark
11 Observatoire de Genève, Chemin des Maillettes 51, 1290 Sauverny, Switzerland

A&A 411, L383 (2003)

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 50-90keV and an optical depth of 1.0-1.3 plus reflection from a cold or mildly ionized slab with a covering factor 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.
Key words: black hole physics - stars: individual: Cyg X-1 - gamma rays: observations - X-rays: binaries - X-rays: general

Preprint (178 kb PDF file including figures)

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