Astron. Astrophys. 353, 847-852 (2000)

HEGRA search for TeV emission from BL Lacertae objects

F.A. Aharonian ¹, A.G. Akhperjanian ⁷, J.A. Barrio ^2,3, K. Bernlöhr ^1.*, H. Bojahr ⁶, I. Calle ³, J.L. Contreras ³, J. Cortina ³, A. Daum ¹, T. Deckers ⁵, S. Denninghoff ², V. Fonseca ³, J.C. Gonzalez ³, G. Heinzelmann ⁴, M. Hemberger ¹, G. Hermann ^1,, M. Heß ¹, A. Heusler ¹, W. Hofmann ¹, H. Hohl ⁶, D. Horns ⁴, A. Ibarra ³, R. Kankanyan ^1,7, M. Kestel ², J. Kettler ¹, C. Köhler ¹, A. Konopelko ^1,, H. Kornmeyer ², D. Kranich ², H. Krawczynski ^1,4, H. Lampeitl ¹, A. Lindner ⁴, E. Lorenz ², N. Magnussen ⁶, O. Mang ⁵, H. Meyer ⁶, R. Mirzoyan ², A. Moralejo ³, L. Padilla ³, M. Panter ¹, D. Petry ^2,6,, R. Plaga ², A. Plyasheshnikov ^1,§, J. Prahl ⁴, G. Pühlhofer ¹, G. Rauterberg ⁵, C. Renault ^1,#, W. Rhode ⁶, A. Röhring ⁴, V. Sahakian ⁷, M. Samorski ⁵, D. Schmele ⁴, M. Schilling ⁵, F. Schröder ⁶, W. Stamm ⁵, H.J. Völk ¹, B. Wiebel-Sooth ⁶, C. Wiedner ¹, M. Willmer ⁵ and W. Wittek <sup>2

1</sup> Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany
² Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München, Germany
³ Universidad Complutense, Facultad de Ciencias Físicas, Ciudad Universitaria, 28040 Madrid, Spain
⁴ Universität Hamburg, II. Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
⁵ Universität Kiel, Institut für Experimentelle und Angewandte Physik, Leibnizstrasse 17-19, 24118 Kiel, Germany
⁶ Universität Wuppertal, Fachbereich Physik, Gaußstrasse 20, 42097 Wuppertal, Germany
⁷ Yerevan Physics Institute, Alikhanian Br. 2, 375036 Yerevan, Armenia
^* Now at Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe, Germany
 Now at Enrico Fermi Institute, University of Chicago, 933 East 56th Street, Chicago, IL 60637, USA
 Now at Universidad Autónoma de Barcelona, Instituto de Física d'Altes Energies, 08193 Bellaterra, Spain
^§ On leave from: Altai State University, Dimitrov Street 66, 656099 Barnaul, Russia
^# Now at LPNHE, Universités Paris VI-VII, 4 place Jussieu, 75252 Paris Cedex 05, France

Received 30 March 1999 / Accepted 12 November 1999

Abstract

The HEGRA system of four Imaging Atmospheric Cherenkov Telescopes (IACTs) has been used to extensively observe extragalactic objects. In this paper we describe the search for TeV emission from nine very promising potential TeV sources, namely eight "high frequency" BL Lac objects (HBLs), and the object "BL Lacertae" itself. These objects were observed during 1997 and 1998 seasons, with total integration times ranging between one and fifteen hours. No evidence for emission was found from any of these objects and the upper limits on the integral energy flux above 750 GeV are on the level of a few times 10^-12 erg cm^-2 s^-1. For the two objects BL Lacertae and 1ES 2344+51.4, we discuss the astrophysical implications of the TeV flux upper limit, using also information from the X-ray and -ray bands as measured with the All Sky Monitor (ASM) of RXTE (1.3-12.0 keV) and with EGRET (30 MeV - 20 GeV).

Key words: galaxies: BL Lacertae objects: general galaxies: BL Lacertae objects: individual: 1 ES 2344+51.4 galaxies: BL Lacertae objects: individual: BL Lac gamma rays: observations

Send offprint requests to: C. Renault (rcecile@in2p3.fr)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Data
• 3. Upper limits in Crab units and in flux units
• 4. Correction for intergalactic absorption
• 5. Experimental results
• 6. BL Lacertae (1ES 2200+42.0)
• 7. 1ES 2344+51.4
• 8. Observational strategy
• 9. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: January 18, 2000
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