A new upper limit on the redshift of PG 1553+113 from observations with the MAGIC Telescope

TL;DR

This study uses MAGIC Telescope observations from 2005 to 2008 to set new upper limits on the redshift of the active galactic nucleus PG 1553+113 by analyzing gamma-ray spectra and accounting for extragalactic background light absorption.

Contribution

It provides the first combined analysis of multiple observation campaigns to constrain the redshift of PG 1553+113 using gamma-ray spectral data.

Findings

Derived new upper limits on the redshift of PG 1553+113.

Compared and combined spectra from different observation periods.

Applied EBL models to correct for gamma-ray absorption.

Abstract

Very high energy gamma ray emission from the active galactic nucleus PG 1553+113 was observed during 2005 and 2006 by the MAGIC collaboration, for a total observation time of 18.8 hours. Here we present the results of follow up observations: more than 20 hours of good quality data collected by the MAGIC Telescope during the 2007 and 2008 campaigns. The obtained spectra are compared and combined with previous measurements, and corrected for absorption adopting different EBL models. Upper limits on the unknown source redshift are derived by assuming the absence of a break in the intrinsic spectrum, or alternatively by constraining the hardness of the intrinsic source spectrum.