H.E.S.S. observations of the Crab during its March 2013 GeV gamma-ray flare

¹ Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
² Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
³ Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, 2 Dublin, Ireland
⁴ National Academy of Sciences of the Republic of Armenia, Yerevan
⁵ Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
⁶ Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
⁷ Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
⁸ University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
⁹ DESY, 15738 Zeuthen, Germany
¹⁰ Institut fürPhysik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam, Germany
¹¹ Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
¹² Department of Physics and Electrical Engineering, Linnaeus University, 351 95 Växjö, Sweden
¹³ Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
¹⁴ Institut für Astro- und Teilchenphysik, Leopold-Franzens-Universität Innsbruck, 6020 Innsbruck, Austria
¹⁵ Laboratoire Leprince-Ringuet, École Polytechnique, CNRS/IN2P3, 91128 Palaiseau, France
¹⁶ Centre for Space Research, North-West University, 2520 Potchefstroom, South Africa
¹⁷ LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
¹⁸ LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, 4 place Jussieu, 75252, Paris Cedex 5, France
¹⁹ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
²⁰ DSM/Irfu, CEA Saclay, 91191 Gif-Sur-Yvette Cedex, France
²¹ Astronomical Observatory, The University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw, Poland
²² now at Harvard-Smithsonian Center for Astrophysics, 60 garden Street, Cambridge MA, 02138, USA
²³ School of Physics, University of the Witwatersrand, 1 Jan Smuts Avenue, Braamfontein, 2050 Johannesburg, South Africa
²⁴ Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany
²⁵ Oskar Klein Centre, Department of Physics, Stockholm University, Albanova University Center, 10691 Stockholm, Sweden
²⁶ Wallenberg Academy Fellow  
²⁷ Université Bordeaux 1, CNRS/IN2P3, Centre d’Études Nucléaires de Bordeaux Gradignan, 33175 Gradignan, France
²⁸ Funded by contract ERC-StG-259391 from the European Community  
²⁹ University of Namibia, Department of Physics, Private Bag 13301, Windhoek, Namibia
³⁰ School of Chemistry & Physics, University of Adelaide, Adelaide 5005, Australia
³¹ APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13, France
³² UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France
³³ Department of Physics and Astronomy, The University of Leicester, University Road, Leicester, LE1 7RH, UK
³⁴ Instytut Fizyki Ja¸drowej PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
³⁵ Laboratoire Univers et Particules de Montpellier, Université Montpellier 2, CNRS/IN2P3, CC 72, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
³⁶ Laboratoire d’Annecy-le-Vieux de Physique des Particules, Université de Savoie, CNRS/IN2P3, 74941 Annecy-le-Vieux, France
³⁷ Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków, Poland
³⁸ Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Toruń, Poland
³⁹ Department of Physics, University of the Free State, PO Box 339, 9300 Bloemfontein, South Africa
⁴⁰ Charles University, Faculty of Mathematics and Physics, Institute of Particle and Nuclear Physics, V Holešovičkách 2, 180 00 Prague 8, Czech Republic

^⋆ Corresponding authors: arnim.balzer@desy.de, dieter.horns@desy.de, kornelia.stycz@desy.de

Received: 8 November 2013
Accepted: 18 January 2014

Abstract

Context. On March 4, 2013 the Fermi-LAT and AGILE reported a flare from the direction of the Crab nebula in which the high-energy (HE; E > 100 MeV) flux was six times above its quiescent level. Simultaneous observations in other energy bands give us hints about the emission processes during the flare episode and the physics of pulsar wind nebulae in general.

Aims. We search for variability in the emission of the Crab nebula at very-high energies (VHE; E > 100 GeV), using contemporaneous data taken with the H.E.S.S. array of Cherenkov telescopes.

Methods. Observational data taken with the H.E.S.S. instrument on five consecutive days during the flare were analysed for the flux and spectral shape of the emission from the Crab nebula. Night-wise light curves are presented with energy thresholds of 1 TeV and 5 TeV.

Results. The observations conducted with H.E.S.S. on March 6 to March 10, 2013 show no significant changes in the flux. They limit the variation in the integral flux above 1 TeV to less than 63% and the integral flux above 5 TeV to less than 78% at a 95% confidence level.