Detection of the Crab Pulsar above 25 GeVwith the MAGIC Cherenkov Telescope

Nepomuk Otte
UC Santa Cruz


In 2005 we observed a 3 sigma excess of pulsed gamma-ray emission from the Crab pulsar with the MAGIC air Cherenkov telescope. The hint of pulsed emission was a driving force to develop a new trigger system, which allowed us to lower the energy threshold of the telescope from 60 GeV to about 25 GeV. With the new trigger system we observed the Crab pulsar between October 2007 and February 2008, and detected the Crab pulsar with a significance of 6.4 standard deviations.

This is the first time that a pulsar has been detected in gamma rays above 25 GeV. It is an important achievement because gamma rays of such energies provide direct information about the non-thermal processes in the magnetosphere of a pulsar.

From previous non-detections above 100 GeV it is known that the spectral energy distribution of the Crab pulsar exhibits a steep
turnover above 10 GeV. The point at which the spectrum turns over and the shape of the turnover provide information about the acceleration of particles in the magnetosphere. I also discuss the pulse profile, and compare it to EGRET data at lower energies.