Egret observations of the diffuse gamma-ray emission in Orion: Analysis through cycle 6

We present a study of the high-energy diffuse emission observed toward Orion by EGRET on the Compton Gamma Ray Observatory. The total exposure by EGRET in this region has increased by more than a factor of 2 since a previous study. A simple model for the diffuse emission adequately fits the data; no significant point sources are detected in the region studied (l = 195 degrees to 220 degrees and b = -25 degrees to -10 degrees) in either the composite data set or in two separate groups of EGRET viewing periods considered. The gamma-ray emissivity in Orion is found to be (1.65 +/- 0.11) x 10(-26) s(-1) sr(-1) for E > 100 MeV, and the differential emissivity is well described as a combination of contributions from cosmic-ray electrons and protons with approximately the local density. The molecular mass calibrating ratio is N(H-2)/W-CO = (1.35 +/- 0.15) x 10(20) cm(-2) (K km s(-1))(-1).