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Observation of TeV gamma rays from the Crab nebula using the atmospheric Cerenkov imaging technique
Weekes, T. C.; Cawley, M. F.; Fegan, D. J.; Gibbs, K. G.; Hillas, A. M.; Kowk, P. W.; Lamb, R. C.; Lewis, D. A.; Macomb, D.; Porter, N. A.; Reynolds, P. T.; Vacanti, G.
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AC(Saint Patrick's College, Maynooth, Republic of Ireland), AD(University College, Dublin, Republic of Ireland), AE(Leeds, University, England)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 342, July 1, 1989, p. 379-395. Research supported by DOE, Smithsonian Scholarly Studies Fund, National Board of Science and Technology of Ireland, and NATO. (ApJ Homepage)
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NASA/STI Keywords:
Cerenkov Counters, Crab Nebula, Gamma Ray Astronomy, Imaging Techniques, Pulsars, Azimuth, Electron Energy, Image Processing, Monte Carlo Method, Periodic Variations, Reflectors, Spectral Energy Distribution
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The Whipple Observatory 10-m reflector, operating as a 37-pixel camera, has been used to observe the Crab Nebula in TeV gamma rays. By selecting gamma-ray images based on their predicted properties, more than 98 percent of the background is rejected; a detection is reported at the 9.0-sigma level, corresponding to a flux of 1.8 x 10 to the -11th photons sq cm/s above 0.7 TeV (with a factor of 1.5 uncertainty in both flux and energy). Less than 25 percent of the observed flux is pulsed at the period of PSR 0531. There is no evidence for variability on time scales from months to years. Although continuum emission from the pulsar cannot be ruled out, it seems more likely that the observed flux comes from the hard Compton synchrotron spectrum of the nebula.

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