$Fermi$-LAT detection of a transient $\gamma$-ray source in the direction of a distant blazar B3 1428+422 at $z =4.72$

TL;DR

This paper reports the detection of a transient gamma-ray source associated with a distant blazar at redshift 4.72, using 110 months of Fermi-LAT data, potentially making it the most distant GeV source observed.

Contribution

First detection of a transient gamma-ray source at such a high redshift, linking it to a distant blazar and providing insights into early universe gamma-ray sources.

Findings

Identified a transient gamma-ray source near B3 1428+422

Suggests the source is the gamma-ray counterpart of a high-redshift blazar

Supports the existence of distant gamma-ray blazars at z=4.72

Abstract

We report the detection of a transient $\gamma$-ray source in the direction of B3 1428+422 ($z=4.72$) by analyzing the 110-month {\it Fermi}-LAT Pass 8 data. The new transient $\gamma-$ray source is far away from the Galactic plane and has a rather soft spectrum, in agreement with being a high redshift blazar. We suggest that the newly discovered transient is the $\gamma$-ray counterpart of B3 1428+422, which could be the {\it most distant} GeV source detected so far. The detection of a group of such distant $\gamma-$ray blazars will be helpful to reconstruct the evolution of the luminosity function and to study the extragalactic background light at such high redshifts.