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Discovery of Gamma‐Ray Emission above 350 GeV from the BL Lacertae Object 1ES 2344+514

M. CataneseDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160C. AkerlofRandall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1120H. M. BadranDepartment of Physics, Faculty of Science, Tanta University, Tanta, EgyptS. D. BillerDepartment of Physics, Oxford University, Oxford, UKI. H. BondDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKP. J. BoyleExperimental Physics Department, University College, Belfield, Dublin 4, IrelandS. M. BradburyDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKJ. H. BuckleyDepartment of Physics, Washington University, St. Louis, MO 63130A. M. BurdettDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKJ. Bussóns GordoExperimental Physics Department, University College, Belfield, Dublin 4, IrelandD. A. Carter‐LewisDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160M. F. CawleyV. ConnaughtonNASA, Marshall Space Flight Center, Huntsville, AL 35812D. J. FeganExperimental Physics Department, University College, Belfield, Dublin 4, IrelandJ. P. FinleyDepartment of Physics, Purdue University, West Lafayette, IN 47907J. A. GaidosDepartment of Physics, Purdue University, West Lafayette, IN 47907T. A. HallDepartment of Physics, Purdue University, West Lafayette, IN 47907A. M. HillasDepartment of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UKF. KrennrichDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160R. C. LambSpace Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125R. W. LessardDepartment of Physics, Purdue University, West Lafayette, IN 47907C. MastersonExperimental Physics Department, University College, Belfield, Dublin 4, IrelandJ. E. McEneryExperimental Physics Department, University College, Belfield, Dublin 4, IrelandG. MohantyDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160J. QuinnPresent address: Department of Physics, University of Utah, Salt Lake City, UT 84112A. 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, UKF. W. SamuelsonDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160M. S. SchubnellRandall Laboratory of Physics, University of Michigan, Ann Arbor, MI 48109-1120G. H. SembroskiDepartment of Physics, Purdue University, West Lafayette, IN 47907R. SrinivasanDepartment of Physics, Purdue University, West Lafayette, IN 47907T. C. WeekesC. WilsonDepartment of Physics, Purdue University, West Lafayette, IN 47907J. ZweerinkDepartment of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160

1998en

ABI

Аннотация

We present the discovery of gamma-ray emission greater than 350 GeV from the BL Lacertae (BL Lac) object 1ES 2344]514 with the Whipple Observatory 10 m gamma-ray telescope. This is the third BL Lac object detected at very high energies (VHE, E [ 300 GeV), the other two being Markarian 421 (Mrk 421) and Mrk 501. These three active galactic nuclei are all X-ray selected and have the lowest known redshifts of any BL Lac objects currently identied with declination greater than 0. The evidence for emission from 1ES 2344]514 comes mostly from an apparent are on 1995 December 20 (UT) during which a 6 p excess was detected with an average ux of I([350 GeV) \ 6.6 ^1.9 ] 10~11 photons cm~2 s~1. This is approximately 63% of the VHE emission from the Crab Nebula, the standard candle in this eld. Observations taken between 1995 October and 1996 January, excluding the night of the are, yield a 4 p detection indicating a ux level of I([350 GeV) \ 1.1 ^0.4 ] 10~11 photons cm~2 s~1, or about 11% of the VHE Crab Nebula ux. Observations taken between 1996 September and 1997 January on this object did not yield a signicant detection of a steady ux or any evidence of aring activity. The 99.9% condence level upper limit from these observations is I([350 GeV) \ 8.2 ] 10~12 photons cm~2 s~1, of the Crab Nebula ux. The low baseline emission level and variation in the [8% nightly and yearly ux of 1ES 2344]514 are the same as the VHE emission characteristics of Mrk 421 and Mrk 501.

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DOI: 10.1086/305857

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