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

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 $γ$-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 $γ$-ray light curves are found to be rather similar, and the strong quasi-simultaneous infrared and $γ$-ray flares are proved to be unique among the nearby $γ$-ray sources. This is the first time to identify a $γ-$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 $γ-$ray flares from some blazars as distant as redshift $\sim$ 5 are expected to be detectable for Fermi-LAT.

13 pages, 4 figures and 1 table, ApJL in press