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

TL;DR

This study reports the detection of gamma-ray emissions from the Crab pulsar above 25 GeV using MAGIC I, revealing spectral features inconsistent with standard models and providing detailed pulse characteristics.

Contribution

First detection of Crab pulsar gamma-ray emission above 25 GeV with MAGIC I, challenging existing spectral models and providing detailed phase and spectral measurements.

Findings

Gamma-ray emission detected between 25 and 100 GeV.

Spectral indices for main pulse and interpulse are approximately -3.1 and -3.5.

Pulse peak positions and widths are precisely measured.

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 2007/2008 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.