Probe of Lorentz Invariance Violation effects and determination of the distance of PG 1553+113

TL;DR

This paper uses high-energy observations of PG 1553+113 to constrain Lorentz invariance violation effects and estimates the source's distance, providing new limits on quantum gravity theories.

Contribution

It introduces a novel method combining H.E.S.S. and Fermi data to better determine the redshift and set constraints on LIV effects in high-energy astrophysics.

Findings

Constraints on Lorentz invariance violation energy scale.

Estimated redshift of PG 1553+113 close to optical measurements.

Detected intra-night variability in VHE flux.

Abstract

The high frequency peaked BL Lac object PG 1553+113 underwent a flaring event in 2012. The High Energy Stereoscopic System (H.E.S.S.) observed this source for two consecutive nights at very high energies (VHE, $E>$100~GeV). The data show an increase of a factor of three of the flux with respect to archival measurements with the same instrument and hints of intra-night variability. The data set has been used to put constraints on possible Lorentz invariance violation (LIV), manifesting itself as an energy dependence of the velocity of light in vacuum, and to set limits on the energy scale at which Quantum Gravity effects causing LIV may arise. With a new method to combine H.E.S.S. and Fermi large area telescope data, the previously poorly known redshift of PG 1555+113 has been determined to be close to the value derived from optical measurements.