On Aug. 5, 1992, BATSE detected the bright soft X-ray transient GRO J0422+32,also known as Nova Per 1992. The COMPTEL instrument (0.75-30MeV) aboard the Compton Gamma-Ray Observatory (CGRO) observed this black-hole candidate twice. During the first observation, which started when the X-ray flux was at its maximum, GRO J0422+32 was detected between 1 and 2MeV. 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 several models that may explain the total hard-X/γ-ray spectrum, including the generalised Comptonisation model from Titarchuk. During the second observation, 3 weeks later, no evidence for emission above 1MeV was seen.
Astronomy and Astrophysics
European Southern Observatory (ESO)
R. van Dijk, K. Bennett, W. Collmar, R. Diehl, W. Hermsen, G.G. Lichti, M. McConnell, J. Ryan, V. Schönfelder, A. Strong, J. van Paradijs, and C. Winkler. THE BLACK-HOLE CANDIDATE GRO J0422+32: MEV EMISSION MEASURED WITH COMPTEL. 1995, Astron. Astrophys., 296, L33.