Pulsed high-energy gamma rays from the Crab Nebula

The Cornell 100-inch gas-Cerenkov y-ray telescope has detected pulsed radiation at hundreds of MeV, up to more than 1 GeV, coincident in time with the optical pulses from NP 0532, and in direction within 1 of the Crab Nebula. Two spectral points lie on an extension of the pulsed X-ray spectrum: the expression 0.95E-'08 keV cm-2 1 keV-1 fits a synthesis of the data from 5 keV to 106 keV. The main pulse and the secondary pulse contain about equal numbers of events and show evidence of being narrower than at lower energies. There is weak evidence for further pulse structure in the interval between these two peaks, and also for an unmodulated y-ray component about equal to the time-averaged pulsed flux. The pulsar and nebular spectra appear to steepen somewhere between 1.5 and 150 GeV. No pulsed flux from NP 0525 was detectable in this flight. Subject headings: Crab Nebula - gamma rays - pulsars