Detection of multi-TeV emission from Markarian 421
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- Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011-3160 (United States)
- Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120 (United States)
- Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, P.O. Box 97, Amado, Arizona 85645-0097 (United States)
- Department of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England (United Kingdom)
- Physics Department, St. Patricks College, Maynooth, County Kildare (Ireland)
- Physics Department, University College, Dublin 4 (Ireland)
- Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States)
Gamma rays with energies exceeding 5{plus_minus}1.5TeV have been detected from Markarian 421 using the Whipple Observatory{close_quote}s 10 m {gamma}-ray telescope. These observations employ a new technique: the so-called large zenith-angle technique. Because they are taken at large zenith angles, the observations yield high statistics data on the multi-TeV part of the spectrum and are well suited for examining the question of a possible energy cutoff. Observations taken during high states on 1995 June 20, 21, and 28 show no evidence for a spectral break. These results conflict with a previous interpretation of the Markarian 421 energy spectrum in which a cutoff due to {gamma}-ray absorption in extragalactic space was postulated. {copyright} {ital 1997} {ital The American Astronomical Society}
- OSTI ID:
- 628693
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 481; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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