Multi-wavelength Variability Properties of CGRaBS J0733+0456: Identifying a Distant Gamma-Ray Blazar at z = 3.01

Abstract

Abstract We report on Owens Valley Radio Observatory (OVRO), WISE, Swift and Fermi-LAT observations of the high redshift blazar CGRaBS J0733+0456, from which significant flux variations in radio and 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 IR and γ-ray flares are proven to be unique among the nearby γ-ray sources. This is the first time that a γ-ray blazar at redshift z ≥ 3 with multi-wavelength flux variations (flares) is identified. Broadband spectral energy distributions in different flux states are constructed and theoretically described. The γ-ray flares from some blazars as distant as redshift ∼5 are expected to be detectable for Fermi-LAT.