VHE gamma-ray measurements of the Crab Nebula and Pulsar by MAGIC

摘要

In the last two years 2010 and 2011 the Crab nebula and its pulsar have surprised the gamma-ray astrophysics community at least twice: the former with GeV flares detected by AGILE and Fermi-LAT, the latter with very high energy (VHE, E > 100 GeV) pulsed emission extending up to 400 GeV detected by MAGIC and VERITAS. These exciting results show that there is still much left to understand about this object. We report here the results of the MAGIC stereoscopic observations of the Crab nebula and pulsar carried on between October 2009 and April 2011. For the nebula, the analysis of these data yields a differential energy spectrum with an unprecedented precision spanning from 50 GeV to 45 TeV, a precise determination of its inverse Compton (IC) peak, and the measurement of the VHE emission during the GeV flare of April 2011. Implications on the modeling of the Crab nebula, especially regarding the strength of the magnetic field, are discussed. For the pulsar, a phase-resolved energy spectrum and a lightcurve in the range 50-400 GeV are obtained. Together with previous MAGIC monoscopic results above 25 GeV they allow for a detailed study of the pulsed VHE emission, which can be interpreted as an additional component due to IC emission from secondary and tertiary pairs on IR-UV photons in the outer magnetosphere.