NEW COMPTEL RESULTS ON MEV GAMMA-RAYS FROM THE ORION MONOCEROS REGION/

We present new COMPTEL observations of the Orion/Monoceros region, con firming our previous report of excessive 3-7 MeV emission which we ten tatively attributed to nuclear deexcitation lines at 4.44 and 6.13 MeV from accelerated C-12 and O-16 nuclei. We show first results from a c ombination of all data obtained during the first five years of the mis sion, with emphasis on the extent of the emission region. The 3-7 MeV radiation is observed at the 9 a significance level with a flux of(12. 8 +/- 1.5) x 10(-5) gamma cm(-2) s(-1), consistent with our previous f indings. In addition, we can firmly conclude now that one single sourc e cannot explain the measured intensity distribution: we find that the emission extends over the complex (the Orion A and B and the Mon R2 c louds), but it may actually be due to a few localized source regions. Evidence (4.4 sigma) for emission from the Mon OB1/OB2 area is appeari ng as well. We present a preliminary spectrum (not fully deconvolved), which indicates that the emission is widely spread over the 3-7 MeV r ange, suggesting a dominantly broad-line origin from energetic C and O nuclei if indeed caused by nuclear lines. The spectrum shows features that might be due to splitting of the C and O lines, but further subs tantiation should come from forthcoming spectral analyses and new obse rvations.