# Multi-wavelength variability of CGRaBS J0733+0456: identifying a distant $\gamma$-ray blazar at z = 3.01

## TL;DR

This study reports multi-wavelength observations of the distant blazar CGRaBS J0733+0456 at redshift 3.01, revealing significant flux variability across radio, IR, and gamma-ray bands, including rapid IR flares, and constructs spectral energy distributions to understand its emission mechanisms.

## Contribution

It is the first to identify a gamma-ray blazar at z ≥ 3 with multi-wavelength flux variations, demonstrating the potential to detect even more distant blazars with Fermi-LAT.

## Key findings

- Significant flux variations detected in radio, IR, and gamma-ray bands.
- IR and gamma-ray flares are quasi-simultaneous and unique among nearby sources.
- Spectral energy distributions constructed for different flux states.

## Abstract

We report on OVRO, WISE, Swift and Fermi-LAT observations of the high redshift blazar CGRaBS J0733+0456, from which significant flux variations in radio, infrared (IR) as well as $\gamma$-ray domains are detected. Particularly, the amplitude of long-term IR variation is over one order of magnitude and the IR variability timescale can be constrained as short as a few hours in the source frame. The IR and $\gamma$-ray light curves are found to be rather similar, and the strong quasi-simultaneous infrared and $\gamma$-ray flares are proved to be unique among the nearby $\gamma$-ray sources. This is the first time to identify a $\gamma-$ray blazar at redshift $z\geq 3$ with multi-wavelength flux variations (flares). Broadband spectral energy distributions in different flux states are constructed and theoretically described. The $\gamma-$ray flares from some blazars as distant as redshift $\sim$ 5 are expected to be detectable for Fermi-LAT.