Hard X-ray detection of XTEJ1755-324 with the SIGMA telescope

We present observations of the X-ray transient XTEJ1755-324 performed durin g september 1997 with the SIGMA hard X-ray telescope onboard the GRANAT obs ervatory. The source was first detected in soft X-rays with XTE on July 25 1997 with a rather soft X-ray spectrum. On September 16 it was first detect ed in hard X-rays by the French soft gamma ray telescope SIGMA during a Gal actic Center observation, The flux was stronger on September 16 and 17 reac hing a level of similar to 110 mCrab in the 40-80 keV energy band while the spectrum could be modeled with a power law with photon index alpha =-2.3+/ - 9.9 (1 sigma error) while the 40-150 keV luminosity was similar to 8 X 10 (36) erg s(-1) for a distance of 8.5 kpc. SIGMA and XTE results on this sou rce indicate that this source had an ultrasoft-like state during its main o utburst and a harder secondary outburst in September. These characteristics make the source similar to X-Nova Muscae 1991, a well known black hole can didate.