Krennrich, F. 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 Lamb, R.C. and Lessard, R.W. and Masterson, C. and McEnery, J.E. and Mohanty, G. and Moriarty, P. and Quinn, J. and Rodgers, A.J. and Rose, H.J. and Samuelson, F.W. and Sembroski, G.H. and Srinivasan, R. and Vassiliev, V.V. and Weekes, T.C. (1999) Measurement of the Multi-TeV Gamma-Ray Flare Spectra of Markarian 421 and Markarian 501. Astrophysical Journal, 511 (149). ISSN 0004-637X

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Abstract

The energy spectrum of Markarian 421 in flaring states has been measured from 0.3 to 10 TeV using both small and large zenith angle observations with the Whipple Observatory 10 m imaging telescope. The large zenith angle technique is useful for extending spectra to high energies, and the extraction of spectra with this technique is discussed. The resulting spectrum of Markarian 421 is fitted reasonably well by a simple power law: J(E)=E−2.54 ± 0.03 ± 0.10 photons m-1 s-1 TeV-1, where the first set of errors is statistical and the second set is systematic. This is in contrast to our recently reported spectrum of Markarian 501, which over a similar energy range has substantial curvature. The differences in TeV energy spectra of gamma-ray blazars reflect both the physics of the gamma-ray production mechanism and possibly differential absorption effects at the source or in the intergalactic medium. Since Markarian 421 and Markarian 501 have almost the same redshift (0.031 and 0.033, respectively), the difference in their energy spectra must be intrinsic to the sources and not due to intergalactic absorption, assuming the intergalactic infrared background is uniform.

Item Type:	Article
Additional Information:	Citation: F. Krennrich et al 1999 ApJ 511 149
Keywords:	BL Lacertae objects: individual; Markarian 421; Markarian 501; galaxies: active; gamma rays: observations;
Academic Unit:	Faculty of Science and Engineering > Experimental Physics
Item ID:	9962
Identification Number:	https://doi.org/10.1086/306677
Depositing User:	Dr. Michael Cawley
Date Deposited:	19 Sep 2018 12:03
Journal or Publication Title:	Astrophysical Journal
Publisher:	American Astronomical Society
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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