Relativistic smearing detected in the spectrum of Cyg X-1 in hard state observed by BeppoSAX

We report on an observation of the black hole candidate Cyg X-1 performed b y the Narrow Field Instruments on board BeppoSAX satellite. During the Bepp oSAX observation Cyg X-1 was in its usual low (hard) state with a 0.1-200 k eV luminosity of similar to 2.6 x 10(37) erg/s, adopting a distance of 2.5 kpc. The broad band spectrum (0.1-30 keV) is well fitted by an absorbed pow er-law partially reflected by cold matter and a soft excess. The reprocesse d component is relativistically smeared and the inferred inner radius of th e disc is 20 +/- 10 gravitational radii. This inner radius is much smaller than the prediction of the so called Advection Dominated Accretion Flow mod els: R-in > 200 R-g.