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Outburst of TeV photons from Markarian 421Markarian 421, an active galactic nucleus (AGN) of the BL Lacertae type, is the closest Energetic Gamma Ray Experiment Telescope (EGRET)-detected AGN. It has been monitored by the Whipple Observatory very high energy gamma-ray telescope since its discovery at TeV energies, for approximately 90 nights, totaling 130 hours of observation. Observations from 1993 December 23 to 1994 May 10 showed an average sourve flux only half that of its 1992 discovery level. However, observations on 1994 May 14 and 15 show an increase in flux above this quiescent level by a factor of approximately 10. The timescale of this increase provides the best geometric constraint on the extent of TeV photon emission regions within AGNs. The observation of the high TeV flux occurred 1 day prior to the observation by ASCA of a very high 2-10 keV X-ray flux. This strong TeV outburst is reminiscent of the behavior seen for the stronger 100 MeV-GeV EGRET sources (e.g. 3C 279) but was not anticipated in view of the fact that the six EGRET observations of Mrk 421 from 1991 June to 1993 July showed no evidence for variability.
Document ID
19950037958
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Kerrick, A. D.
(Iowa State Univ. Ames, IA, United States)
Akerlof, C. W.
(Univ. of Michigan, Ann Arbor, MI United States)
Biller, S. D.
(Univ. of Leeds Leeds, United Kingdom)
Buckley, J. H.
(Harvard-Smithsonian Center for Astrophysics, Amado, AZ United States)
Cawley, M. F.
(St. Patrick's College Maynooth, County Kildare, United Kingdom)
Chantell, M.
(Harvard-Smithsonian Center for Astrophysics, Amado, AZ United States)
Connaughton, V.
(Univ. College Dublin Belfield, Dublin, United Kingdom)
Fegan, D. J.
(Univ. College Dublin Belfield, Dublin, United Kingdom)
Fennell, S.
(Univ. College Dublin Belfield, Dublin, United Kingdom)
Gaidos, J. A.
(Purdue Univ. West Lafayette, IN, United States)
Date Acquired
August 16, 2013
Publication Date
January 10, 1995
Publication Information
Publication: Astrophysical Journal, Part 2 - Letters
Volume: 438
Issue: 2
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A69557
Distribution Limits
Public
Copyright
Other

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