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PG 1553+113: five years of observations with MAGIC
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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 $\pm$ 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/LAT 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 very high energies with archival data available for other wavelengths. The mean spectral energy distribution can be modeled with a one-zone Synchrotron Self Compton (SSC) model, which gives the main physical parameters governing the VHE emission in the blazar jet.
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PAREDES I POY, Josep Maria, RIBÓ GOMIS, Marc and MUNAR I ADROVER, Pere. PG 1553+113: five years of observations with MAGIC. Astrophysical Journal. 2012. Vol. 748, num. 1, pags. 46A. ISSN 0004-637X. [consulted: 11 of August of 2026]. Available at: https://hdl.handle.net/2445/150423