The MAGIC view of PG 1553+113

TL;DR

This study presents five years of MAGIC telescope observations of PG 1553+113, revealing modest variability in VHE gamma-ray flux and a correlated optical variability, and models the source's emission with a one-zone SSC model.

Contribution

It provides the longest VHE observational dataset for PG 1553+113 and combines multi-wavelength data to model its emission mechanisms.

Findings

VHE flux shows marginal variability over three years.

Optical and VHE gamma-ray variability are correlated.

The SED is well modeled by a one-zone SSC model.

Abstract

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.