Aleksic, J.J.AleksicAlvarez, E. A.E. A.AlvarezAntonelli, Lucio AngeloLucio AngeloAntonelliCarosi, AlessandroAlessandroCarosi2020-09-172020-09-172012-03-01https://hdl.handle.net/20.500.13025/2664The Astrophysical Journal, Volume 748, Issue 1, article id. 46, <NUMPAGES>10</NUMPAGES> pp. (2012).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; E > 100 GeV). Power-law fits of the individual years are compatible with a steady mean photon index Gamma = 4.27 0.14. In the last three years of data, the flux level above 150 GeV shows a clear variability (probability of constant flux < 0.001%). The flux variations are modest, lying in the range from 4% to 11% of the Crab Nebula flux. 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) simultaneous Fermi/Large Area Telescope data of PG 1553+113 above 1 GeV, which reveals hints of variability in the 2008-2009 sample. Finally, we present a combination of the mean spectrum measured at VHEs with archival data available for other wavelengths. The mean spectral energy distribution can be modeled with a one-zone synchrotron self-Compton model, which gives the main physical parameters governing the VHE emission in the blazar jet.BL Lacertae objects individual PG 1553+113gamma rays galaxiesradiation mechanisms non-thermal10.1088/0004-637X/748/1/46http://adsabs.harvard.edu/abs/2012ApJ...748...46A2012ApJ...748...46A