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Observations of the Crab pulsar between 25 and 100 GeV with the MAGIC I telescope

We report on the observation of gamma-rays above 25 GeV 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 100 MeV to 100 GeV, 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 100 GeV, 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 while the full widths at half maximum are 0.025 +- 0.008 and 0.053 +- 0.015, respectively.

Gamma rays: stars; pulsars: individual (Crab pulsar; PSR B0531+21)

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