X-RAY-SPECTRUM OF THE BLACK-HOLE CANDIDATE X1755-338

We report the first detection of a hard power-law tail in the X-ray sp ectrum of the black hole candidate (BHC) binary X1755-338, which was o bserved in 1989 March-September during the TTM Galactic Centre Survey. In addition, an ultrasoft thermal component with a temperature of sim ilar to 1.1-1.4 keV was also detected. We demonstrate that the soft an d hard X-ray components of X1755-338 vary independently, as in the spe ctra of the well-known BHCs LMC X-1, LMC X-3 and GX339-4 in their high (intensity) state, If the hard tail observed from X1755-338 is genera ted near the black hole by energetic electrons upscattering low-energy photons, the uncorrelated variations imply that the soft X-rays from the accretion disc may not be the main photon seeds needed for inverse Comptonization The TTM observations strongly suggest that X1755-338 d oes indeed belong to the family of BHCs.