Samuelson, F.W. and Biller, S.D. and Bond, I.H. and Boyle, P.J. and Bradbury, S.M. and Breslin, A.C. and Buckley, J.H. and Burdett, A.M. and Bussons Gordo, J. and Carter-Lewis, D.A. and Catanese, M. and Cawley, Michael F. and Fegan, D.J. and Finley, J.P. and Gaidos, J.A. and Hall, T. and Hillas, A.M. and Krennrich, F. and Lamb, R.C. and Lessard, R.W. and McEnery, J.E. and Masterson, C. and Quinn, J. and Rodgers, A.J. and Rose, H.J. and Sembroski, G.H. and Srinivasan, R. and Vassiliev, V.V. and Weekes, T.C. and Zweerink, J. (1998) The TeV Spectrum of Markarian 501. Astrophysical Journal Letters, 501 (L17). ISSN 0004-637X

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Abstract

The energy spectrum of the active galactic nucleus Markarian 501 has been determined from 0.3 to 10 TeV with the Whipple Observatory Cerenkov Imaging Telescope, by using both small zenith angle and large zenith angle data taken between 1997 February 14 and June 8. The TeV emission from Mrk 501 was unprecedentedly high, allowing a statistically accurate spectrum to be derived. In contrast to previously measured TeV spectra, the spectrum over this energy region is not well described by a simple power law. Instead, the spectrum exhibits significant curvature and can be well fitted by a parabolic spectrum proportional to E-2.22 ± 0.04 ± 0.05 - (0.47 ± 0.07) log10E, where the first set of errors is statistical and the second systematic and E is in units of TeV. Simple power-law fits to the TeV data are also inconsistent with upper limits from EGRET observations that temporally overlap a subset of the TeV observations. The data show a statistically significant signal above energies of 7 TeV. This energy, combined with variability timescales, yields a Doppler beaming factor, δ, of at least 1.5.

Item Type:	Article
Additional Information:	Citation: F. W. Samuelson et al 1998 ApJ 501 L17
Keywords:	BL Lacertae objects: individual; Markarian 501; gamma rays: observations;
Academic Unit:	Faculty of Science and Engineering > Experimental Physics
Item ID:	9966
Identification Number:	https://doi.org/10.1086/311454
Depositing User:	Dr. Michael Cawley
Date Deposited:	19 Sep 2018 14:00
Journal or Publication Title:	Astrophysical Journal Letters
Publisher:	IOP Publishing
Refereed:	Yes
URI:	http://iopscience.iop.org
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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