DETECTION OF GAMMA-RAYS OF UP TO 50 TEV FROM THE CRAB-NEBULA

Gamma rays with energies greater than 7 TeV from the Crab pulsar/Crab Nebula have been observed at large zenith angles, with the imaging atm ospheric technique from Woomera, South Australia. CANGAROO data taken in 1992, 1993, and 1995 indicate that the energy spectrum extends up t o at least 50 TeV, without a change of the index of the power-law spec trum. The observed differential spectrum is (2.01 +/- 0.36) x 10(-13)( E/7w TeV)(-2.53+/-0.18) TeV-1 cm(-2) s(-1) between 7 and 50 TeV. There is no apparent cutoff. The spectrum for photon energies above similar to 10 TeV allows the maximum particle acceleration energy to be infer red and implies that this unpulsed emission does not originate pear th e light cylinder of the pulsar but in the nebula, where the magnetic f ield is not strong enough to allow pair creation from the TeV photons. The hard gamma-ray energy spectrum above 10 TeV also provides informa tion about the varying role of seed photons for the inverse Compton pr ocess at these high energies, as well as a possible contribution of pi (o) gamma rays from proton collisions.