THE BLACK-HOLE CANDIDATE GRO J0422- MEV EMISSION MEASURED WITH COMPTEL(32 )

On Aug. 5, 1992, BATSE detected the bright soft X-ray transient GRO J0 422+32, also known as Nova Per 1992. The COMPTEL instrument (0.75-30 M eV) aboard the Compton Gamma-Ray Observatory (CGRO) observed this blac k-hole candidate twice. During the first observation, which started wh en the X-ray flux was at its maximum, GRO J0422+32 was detected betwee n 1 and 2 MeV. The flux in this energy range was higher than expected from an extrapolation of the standard Sunyaev-Titarchuk Comptonisation model fits to the contemporaneous OSSE and SIGMA data. We discuss sev eral models that may explain the total hard-X/gamma-ray spectrum, incl uding the generalised Comptonisation model from Titarchuk. During the second observation, 3 weeks later, no evidence for emission above 1 Me V was seen.