Detection of Gamma Rays with [ITAL]E[/ITAL] ] 300 GeV from Markarian 501
J. QuinnFred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, P.O. Box 97, Amado, AZ 85645-0097C. AkerlofRandall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1120S. D. BillerDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKJ. H. BuckleyFred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, P.O. Box 97, Amado, AZ 85645-0097D. A. Carter‐LewisDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160M. F. CawleyM. CataneseDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160V. ConnaughtonFred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, P.O. Box 97, Amado, AZ 85645-0097D. J. FeganPhysics Department, University College, Dublin 4, IrelandJ. P. FinleyDepartment of Physics, Purdue University, West Lafayette, IN 47907J. A. GaidosDepartment of Physics, Purdue University, West Lafayette, IN 47907A. M. HillasDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKR. C. LambDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160F. KrennrichDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160R. W. LessardPhysics Department, University College, Dublin 4, IrelandJ. E. McEneryPhysics Department, University College, Dublin 4, IrelandD. I. MeyerRandall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1120G. MohantyDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160A. J. RodgersDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKH. J. RoseDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKM. SchubnellRandall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1120G. SembroskiDepartment of Physics, Purdue University, West Lafayette, IN 47907T. C. WeekesFred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, P.O. Box 97, Amado, AZ 85645-0097C. WilsonDepartment of Physics, Purdue University, West Lafayette, IN 47907J. ZweerinkDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160
1996en
ABI
Abstract
The detection of gamma rays of energy greater than 300 GeV from the BL Lacertae object Mrk 501 demonstrates that extragalactic TeV emission is not unique to Mrk 421. During 66 hr of observations between 1995 March and July we measured an average flux of 8.1 ± 1.4 × 10-12 cm-2 s-1 above 300 GeV, a flux that is only 20% of the average Mrk 421 flux. The new gamma-ray source has not been reported by the Compton Gamma Ray Observatory as an emitter of gamma rays at lower energies. There is evidence for variability on timescales of days.
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