Integral observation of Cyg X-1 in an intermediate state

Abstract

We present preliminary results of an observation of Cygnus X-1 with INTEGRAL performed on June 7-11 2003. Both spectral and variability properties of the source indicate that Cygnus X-1 was in an intermediate state. As expected during state transitions, we find an anticorrelation between the 3-10 keV and the 15 GHz radio fluxes and a strong correlation between the 3-200 keV hardness and radio flux.

4 pages, 8 figures, to appear in the proceedings of the 5th INTEGRAL workshop "The INTEGRAL Universe", (Munich, February 2004), ESA Special Publication SP-552