We report \sim 600 days of BATSE earth-occultation observations of the total gamma-ray ( 30 keV to 1.7 MeV ) emission from the Crab nebula , between 1991 May 24 ( TJD 8400 ) and 1994 October 2 ( TJD 9627 ) .
Lightcurves from { 35–100 , 100–200 , 200–300 , 300–400 , 400–700 , and 700–1000 } keV , show that positive fluxes were detected by BATSE in each of these six energy bands at significances of approximately { 31 , 20 , 9.2 , 4.5 , 2.6 , and 1.3 } \sigma respectively per day .
We also observed significant flux and spectral variations in the 35–300 keV energy region , with time scales of days to weeks .
The spectra below 300 keV , averaged over typical CGRO viewing periods of 6–13 days , can be well described by a broken power law with average indices of \sim 2.1 and \sim 2.4 varying around a spectral break at \sim 100 keV .
Above 300 keV , the long-term averaged spectra , averaged over three 400 d periods ( TJD 8400-8800 , 8800-9200 , and 9200-9628 , respectively ) are well represented by the same power law with index of \sim 2.34 up to \sim 670 keV , plus a hard spectral component extending from \sim 670 keV to \sim 1.7 MeV , with a spectral index of \sim 1.75 .
The latter component could be related to a complex structure observed by COMPTEL in the 0.7-3 MeV range .
Above 3 MeV , the extrapolation of the power-law continuum determined by the low-energy BATSE spectrum is consistent with fluxes measured by COMPTEL in the 3-25 MeV range , and by EGRET from 30-50 MeV .
We interpret these results as synchrotron emission produced by the interaction of particles ejected from the pulsar with the field in different dynamical regions of the nebula system , as observed recently by HST , XMM-Newton , and Chandra .