Observations of the Crab Pulsar between 25 and 100 GeV with the MAGIC I Telescope (original) (raw)

Astrophysical Journal, 2011

Abstract

We report on the observation of γ-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 full widths at half-maximum are 0.025 ± 0.008 and 0.053 ± 0.015, respectively.

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