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

Abstract

We report on the observation of ${\hat{I}}^3$-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 {\it Fermi} Large Area Telescope ({\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.

14 pages, 15 figures, published in Astrophysical Journal