A&A 384, L23-L26 (2002)
DOI: 10.1051/0004-6361:20020206

Letter

TeV gamma rays from the blazar H 1426+428 and the diffuse extragalactic background radiation

F. Aharonian¹, A. Akhperjanian², J. Barrio³, M. Beilicke⁴, K. Bernlöhr¹, H. Börst⁵, H. Bojahr⁶, O. Bolz¹, J. Contreras⁷, R. Cornils⁴, J. Cortina⁷, S. Denninghoff⁷, V. Fonseca³, M. Girma¹, J. Gonzalez³, N. Götting⁴, G. Heinzelmann⁴, G. Hermann¹, A. Heusler¹, W. Hofmann¹, D. Horns¹, I. Jung¹, R. Kankanyan¹, M. Kestel⁷, J. Kettler¹, A. Kohnle¹, A. Konopelko¹, H. Kornmeyer⁷, D. Kranich⁷, H. Krawczynski^{1, 8}, H. Lampeitl¹, M. Lopez³, E. Lorenz⁷, F. Lucarelli³, N. Magnussen⁶, O. Mang⁵, H. Meyer⁶, R. Mirzoyan⁷, A. Moralejo³, E. Ona³, L. Padilla³, M. Panter¹, R. Plaga⁷, A. Plyasheshnikov^{1, 9}, G. Pühlhofer¹, G. Rauterberg⁵, A. Röhring⁴, W. Rhode⁶, J. Robrade⁴, G. Rowell¹, V. Sahakian², M. Samorski⁵, M. Schilling⁵, F. Schröder⁶, I. Sevilla³, M. Siems⁵, W. Stamm⁵, M. Tluczykont⁴, H. J. Völk¹, C. A. Wiedner¹ and W. Wittek<sup>7

1</sup>  Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany
²  Yerevan Physics Institute, Alikhanian Br. 2, 375036 Yerevan, Armenia
³  Universidad Complutense, Facultad de Ciencias Físicas, Ciudad Universitaria, 28040 Madrid, Spain
⁴  Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
⁵  Universität Kiel, Institut für Experimentelle und Angewandte Physik, Leibnizstraße 15-19, 24118 Kiel, Germany
⁶  Universität Wuppertal, Fachbereich Physik, Gaußstr. 20, 42097 Wuppertal, Germany
⁷  Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München, Germany
⁸  Now at Yale University, P.O. Box 208101, New Haven, CT 06520-8101, USA
⁹  On leave from Altai State University, Dimitrov Street 66, 656099 Barnaul, Russia

(Received 21 December 2001 / Accepted 5 February 2002 )

Abstract
The detection of TeV -rays from the blazar H 1426+428 at an integral flux level of above 1 TeV with the HEGRA imaging atmospheric Cherenkov telescope system is reported. H 1426+428 is located at a redshift of z = 0.129, which makes it the most distant source detected in TeV -rays so far. The TeV radiation is expected to be strongly absorbed by the diffuse extragalactic background radiation (DEBRA). The observed energy spectrum of TeV photons is in good agreement with an intrinsic power law spectrum of the source corrected for DEBRA absorption. Statistical errors as well as uncertainties about the intrinsic source spectrum, however, do not permit strong statements about the density of the DEBRA infrared photon field.

Key words: BL Lacertae objects: individual: H 1426+428 -- gamma rays: observations -- diffuse radiation

Offprint request: G. Pühlhofer, Gerd.Puehlhofer@mpi-hd.mpg.de

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© ESO 2002

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