Observations of the Crab Pulsar between 25 and 100gev with the Magic I Telescope

We report on the observation of γ-rays above 25GeV from the Crab pulsar (PSR B0532+21) using the MAGIC I telescope. Two data sets from observations during the winter period 2007/2008 and 2008/2009 are used. In order to discuss the spectral shape from 100MeV to 100GeV, one year of public Fermi Large Area Telescope (Fermi-LAT) data are also analyzed to complement the MAGIC data. The extrapolation of the exponential cutoff spectrum determined with the Fermi-LAT data is inconsistent with MAGIC measurements, which requires a modification of the standard pulsar emission models. In the energy region between 25 and 100GeV, the emission in the P1 phase (from −0.06 to 0.04, location of the main pulse) and the P2 phase (from 0.32 to 0.43, location of the interpulse) can be described by power laws with spectral indices of −3.1±1.0stat±0.3syst and −3.5±0.5stat±0.3syst, respectively. Assuming an asymmetric Lorentzian for the pulse shape, the peak positions of the main pulse and the interpulse are estimated to be at phases −0.009 ± 0.007 and 0.393 ± 0.009, while the full widths at half-maximum are 0.025± 0.008 and 0.053± 0.015, respectively. Subject headings: Gamma rays: stars — pulsars: individual (Crab pulsar, PSR B0531+21) 1 IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra, Spain 2 Universidad Complutense, E-28040 Madrid, Spain 3 INAF National Institute for Astrophysics, I-00136 Rome, Italy 4 Università di Siena, and INFN Pisa, I-53100 Siena, Italy 5 Technische Universität Dortmund, D-44221 Dortmund, Germany 6 Università di Padova and INFN, I-35131 Padova, Italy 7 Inst. de Astrof́ısica de Canarias, E-38200 La Laguna, Tenerife, Spain 8 Depto. de Astrof́ısica, Universidad de La Laguna, E-38206 La Laguna, Spain 9 University of Lódź, PL-90236 Lodz, Poland 10 Tuorla Observatory, University of Turku, FI-21500 Piikkiö, Finland 11 Deutsches Elektronen-Synchrotron (DESY), D-15738 Zeuthen, Germany 12 ETH Zurich, CH-8093 Zurich, Switzerland 13 Max-Planck-Institut für Physik, D-80805 München, Germany 14 Universität Würzburg, D-97074 Würzburg, Germany 15 Universitat de Barcelona (ICC/IEEC), E-08028 Barcelona, Spain 16 Università di Udine, and INFN Trieste, I-33100 Udine, Italy 17 Institut de Ciències de l’Espai (IEEC-CSIC), E-08193 Bellaterra, Spain 18 Inst. de Astrof́ısica de Andalućıa (CSIC), E-18080 Granada, Spain 19 Croatian MAGIC Consortium, Rudjer Boskovic Institute, University of Rijeka and University of Split, HR-10000 Zagreb, Croatia 20 Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain 21 Inst. for Nucl. Research and Nucl. Energy, BG-1784 Sofia, Bulgaria 22 University of California, Santa Cruz, CA 95064, USA 23 INAF/Osservatorio Astronomico and INFN, I-34143 Trieste, Italy 24 Università dell’Insubria, Como, I-22100 Como, Italy 25 Università di Pisa, and INFN Pisa, I-56126 Pisa, Italy 26 ICREA, E-08010 Barcelona, Spain 27 Universitetet i Oslo, N-0313, Oslo, Norway 28 ASIAA/National Tsing Hua University-TIARA, P.O. Box 23-141, Taipei, Taiwan 29 now at: Ecole polytechnique fédérale de Lausanne (EPFL),