The MAGIC view of PG 1553+113
  We present the results of five years (2005-2009) of MAGIC observations of the BL Lac object PG 1553+113 at very high energies (VHEs). Adding the new data set (2007-2009) to previous observations, this source becomes one of the best long-term followed sources at energies above 100 GeV. In the last three years of data, the flux level above 150 GeV shows a marginal variability. Simultaneous optical data also show only modest variability that seems to be correlated with VHE gamma-ray variability. We also performed a temporal analysis of all available Fermi/LAT data of PG 1553+113 above 1 GeV. Finally, we present a combination of the mean spectrum measured at VHE with archival data available for other wavelengths. The mean Spectral Energy Distribution (SED) can be modeled with a one-zone SSC model, which gives the main physical parameters governing the VHE emission in the blazar jet. 
E. Prandini and F. Tavecchio (for the MAGIC Collaboration), S. Buson   and S. Larsson (for the Fermi/LAT Collaboration)
astro-ph.HE