The Crab and Vela gamma ray nebulae

COMPTEL/EGRET observations of the Crab unpulsed component indicates that the 1-150 MeV emission is variable with a photon spectrum of the form ∼ E^-1.7 exp(-E/25 MeV), which does not connect smoothly with the spectrum outside this interval. This hints at an independent synchrotron emission feature in the Crab Nebula. The flux in the 0.3 - 10 GeV interval is a factor ∼ 3 larger than the predicted inverse Compton flux, which indicates that the field in the outer nebula decreases faster than predicted by MHD flow soultions. The OSSE detection of the Vela SNR is (spectrally) consistent with emission from the l′ radius compact nebula. The EGRET upper limit constrains the maximum particle energy in this compact nebula to values below the full polar cap potential drop. However, inverse Compton emission from the Vela X radio nebula is also expected in the EGRET range, leading to a constraint on the radio break frequency and nebular magnetic field strength.