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Originally published in Science Express on 26 October 2006
Science 1 December 2006:
Vol. 314. no. 5804, pp. 1424 - 1427
DOI: 10.1126/science.1134408
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Reports

Fast Variability of Tera–Electron Volt {gamma} Rays from the Radio Galaxy M87

F. Aharonian,1 A. G. Akhperjanian,2 A. R. Bazer-Bachi,3 M. Beilicke,4* W. Benbow,1 D. Berge,1 K. Bernlöhr,1,5 C. Boisson,6 O. Bolz,1 V. Borrel,3 I. Braun,1 A. M. Brown,7 R. Bühler,1 I. Büsching,8 S. Carrigan,1 P. M. Chadwick,7 L.-M. Chounet,9 G. Coignet,10 R. Cornils,4 L. Costamante,1,23 B. Degrange,9 H. J. Dickinson,7 A. Djannati-Ataï,11 L. O'C. Drury,12 G. Dubus,9 K. Egberts,1 D. Emmanoulopoulos,13 P. Espigat,11 F. Feinstein,14 E. Ferrero,13 A. Fiasson,14 G. Fontaine,9 Seb. Funk,5 S. Funk,1 M. Füßling,5 Y. A. Gallant,14 B. Giebels,9 J. F. Glicenstein,15 P. Goret,15 C. Hadjichristidis,7 D. Hauser,1 M. Hauser,13 G. Heinzelmann,4 G. Henri,16 G. Hermann,1 J. A. Hinton,1,13 A. Hoffmann,17 W. Hofmann,1 M. Holleran,8 S. Hoppe,1 D. Horns,17 A. Jacholkowska,14 O. C. de Jager,8 E. Kendziorra,17 M. Kerschhaggl,5 B. Khélifi,9,1 Nu. Komin,14 A. Konopelko,5{dagger} K. Kosack,1 G. Lamanna,10 I. J. Latham,7 R. Le Gallou,7 A. Lemière,11 M. Lemoine-Goumard,9 J.-P. Lenain,6 T. Lohse,5 J. M. Martin,6 O. Martineau-Huynh,18 A. Marcowith,3 C. Masterson,1,23 G. Maurin,11 T. J. L. McComb,7 E. Moulin,14 M. de Naurois,18 D. Nedbal,19 S. J. Nolan,7 A. Noutsos,7 K. J. Orford,7 J. L. Osborne,7 M. Ouchrif,18,23 M. Panter,1 G. Pelletier,16 S. Pita,11 G. Pühlhofer,13 M. Punch,11 S. Ranchon,10 B. C. Raubenheimer,8 M. Raue,4 S. M. Rayner,7 A. Reimer,20 J. Ripken,4 L. Rob,19 L. Rolland,15 S. Rosier-Lees,10 G. Rowell,1 V. Sahakian,2 A. Santangelo,17 L. Saugé,16 S. Schlenker,5 R. Schlickeiser,20 R. Schröder,20 U. Schwanke,5 S. Schwarzburg,17 S. Schwemmer,13 A. Shalchi,20 H. Sol,6 D. Spangler,7 F. Spanier,20 R. Steenkamp,21 C. Stegmann,22 G. Superina,9 P. H. Tam,13 J.-P. Tavernet,18 R. Terrier,11 M. Tluczykont,9,23 C. van Eldik,1 G. Vasileiadis,14 C. Venter,8 J. P. Vialle,10 P. Vincent,18 H. J. Völk,1 S. J. Wagner,13 M. Ward7

The detection of fast variations of the tera–electron volt (TeV) (1012 eV) {gamma}-ray flux, on time scales of days, from the nearby radio galaxy M87 is reported. These variations are about 10 times as fast as those observed in any other wave band and imply a very compact emission region with a dimension similar to the Schwarzschild radius of the central black hole. We thus can exclude several other sites and processes of the {gamma}-ray production. The observations confirm that TeV {gamma} rays are emitted by extragalactic sources other than blazars, where jets are not relativistically beamed toward the observer.

1 Max-Planck-Institut für Kernphysik, Post Office Box 103980, D 69029 Heidelberg, Germany.
2 Yerevan Physics Institute, 2 Alikhanian Brothers Street, 375036 Yerevan, Armenia.
3 Centre d'Etude Spatiale des Rayonnements, CNRS/UPS, 9 avenue du Colonel Roche, BP 4346, F-31029 Toulouse Cedex 4, France.
4 Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, D 22761 Hamburg, Germany.
5 Institut für Physik, Humboldt-Universität zu Berlin, Newtonstrasse 15, D 12489 Berlin, Germany.
6 Laboratoire Univers et Théories, UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, F-92195 Meudon Cedex, France.
7 University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK.
8 Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa.
9 Laboratoire Leprince-Ringuet, IN2P3/CNRS, Ecole Polytechnique, F-91128 Palaiseau, France.
10 Laboratoire d'Annecy-le-Vieux de Physique des Particules, IN2P3/CNRS, 9 Chemin de Bellevue, BP 110 F-74941 Annecy-le-Vieux Cedex, France.
11 Astro Particule et Cosmologie, UMR 7164 (Université Paris 7, CNRS, CEA, Observatoire de Paris), 10 rue Alice Domon et Léonie Duquet, 75025 Paris Cedex 13, France.
12 Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland.
13 Landessternwarte, Universität Heidelberg, Königstuhl, D 69117 Heidelberg, Germany.
14 Laboratoire de Physique Théorique et Astroparticules, IN2P3/CNRS, Université Montpellier II, CC 70, Place Eugène Bataillon, F-34095 Montpellier Cedex 5, France.
15 DAPNIA/DSM/CEA, CE Saclay, F-91191 Gif-sur-Yvette Cedex, France.
16 Laboratoire d'AstrophysiquedeGrenoble, Institut National des Sciences de l'Univers/CNRS, Université Joseph Fourier, BP 53, F-38041 Grenoble Cedex 9, France.
17 Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, D 72076 Tübingen, Germany.
18 Laboratoire de Physique Nucléaire et de Hautes Energies, IN2P3/CNRS, Universités Paris VI and VII, 4 Place Jussieu, F-75252 Paris Cedex 5, France.
19 Institute of Particle and Nuclear Physics, Charles University, V Holesovickach 2, 180 00 Prague 8, Czech Republic.
20 Institut für Theoretische Physik, Lehrstuhl IV, Weltraum und Astrophysik, Ruhr-Universität Bochum, D 44780 Bochum, Germany.
21 University of Namibia, Private Bag 13301, Windhoek, Namibia.
22 Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, D 91058 Erlangen, Germany.
23 European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and Max-Planck-Gesellschaft.

{dagger} Present address: Purdue University, Department of Physics, 525 Northwestern Avenue, West Lafayette, IN 47907–2036, USA.

* To whom correspondence should be addressed. E-mail: matthias.beilicke{at}desy.de

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Radio Imaging of the Very-High-Energy {gamma}-Ray Emission Region in the Central Engine of a Radio Galaxy.
The VERITAS Collaboration, the VLBA 43 GHz M87 Monitoring Team, the H.E.S.S. Collaboration, and the MAGIC Collaboration (2009)
Science 325, 444-448
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The Very-High-Energy Gamma-Ray Sky.
F. Aharonian (2007)
Science 315, 70-72
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