Fermi Gamma-ray Space Telescope

TeraelectronVolts pulsed emission from the Crab detected by MAGIC

Roberta Zanin


The last six years witness several major revisions of our knowledge about the Crab pulsar, the central engine of the remnant of the supernova explosion occurred in 1054 AD. The consensus scenario has been challenged for the origin of the high-energy pulsed emission with the discovery of a very-high-energy power law tail extending up to 400 GeV. This is above the expected spectral cut off of a few GeV. New measurements obtained by the MAGIC collaboration, with more than 300 hours of observations, extend the energy spectrum of the Crab pulsar to ~2 TeV with no evidence of energy cut off. Above 400 GeV the detected emission mainly comes from the interpulse: the pulse profile shows only one significant (at 6.5 sigma level) peak. These findings favor TeV gamma-ray production via inverse Compton scattering close to or beyond the light cylinder radius by either secondary e+- pairs or electrons in the wind. The first case requires a decoupling between electrons and positrons in the surrounding of the light cylinder, while the second case points to a slow and continuous acceleration of the wind up to distances of ~70 light cylinder radius (RLC=10^8 cm).