Detection of pulsed gamma-ays above 25 GeV from the Crab pulsar

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  • 17 September 2008
Abstract
One fundamental unanswered question about pulsars concerns the mechanism of their pulsed electromagnetic radiation. Measuring the high end region of a pulsar's spectrum would shed light on this question, but has challenged ground- based experiments for three decades. By developing a new type of electronic trigger, we could lower the threshold of the MAGIC Cherenkov telescope to 25 GeV, a major breakthrough for this kind of instrument. We detected pulsed gamma-ays from the Crab above 25 GeV, revealing a relatively high energy cut-off in the phase-averaged spectrum. This indicates that emission happens far out in the magnetosphere. Also, the main-pulse and secondary pulse have similar amplitudes at 25 GeV. These results exclude the polar cap model and challenge the slot gap emission model for Crab.

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