1986•The Astrophysical JournalRequires access
Pulsed TeV gamma rays detected from Hercules X-1 during X-ray source eclipse
P. W. Gorham, M. F. Cawley, D. J. Fegan, K. Gibbs, R. C. Lamb, D. F. Liebing, N. A. Porter, V. J. Stenger, T. C. Weekes
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Abstract
Distinct 0.808-Hz pulsations were detected from Her X-1 in June 1985 using the atmospheric Cerenkov technique with the Whipple Observatory 10 m gamma-ray telescope, which had an effective gamma-ray energy threshold of about 600 GeV. The 2-hr observation spanned the transition into X-ray eclipse, at which the X-ray source Her X-1 is first occulted by the companion star HZ Herculis at orbital phase about 0.93 in the binary system. The pulsation persists for 1 hr or more after the beginning of the 6-hr eclipse, and it is concluded that the gamma-ray production site is in this case not coincident with the X-ray source.