| Abstract: | 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 2007/08 and 2008/9 are used. In order to
discuss the spectral shape from 100,MeV to 100,GeV, one year of public {it
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 $-3.1 pm 1.0_{stat}
pm 0.3_{syst}$ and $-3.5 pm 0.5_{stat} pm 0.3_{syst}$, 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 $-0.009 pm
0.007$ and $0.393 pm 0.009$, while the full widths at half maximum are $0.025
pm 0.008$ and $0.053 pm 0.015$, respectively. |
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