Detection of vhe radiation from the bl lac pg 1553+ 113 with the magic telescope
Journal
ApJ Letters ApJ Letters 654 (2007) L119 - L122 654, L119 - L122, 2007
Abstract:
In 2005 and 2006, the MAGIC telescope has observed very high energy gamma-ray emission from the distant BL Lac object PG 1553+113. The overall significance of the signal is 8.8 sigma for 18.8h observation time. The light curve shows no significant flux variations on a daily time-scale, the flux level during 2005 was, however, significantly higher compared to 2006. The differential energy spectrum between ~90 GeV and 500 GeV is well described by a power law with photon index Gamma = 4.2 +- 0.3. The combined 2005 and 2006 energy spectrum provides an upper limit of z=0.74 on the redshift of the object.