Fast γ-Ray Variability in Blazars beyond Redshift 3

High-redshift blazars are one of the most powerful sources in the universe and gamma-ray variability carries crucial information about their relativistic jets. In this wor gamma we present results of the first systematical temporal analysis of Fermi-LAT data of all known seven gamma-ray blazars beyond redshift 3. Significant long-term.-ray variability is found from five sources in monthly gamma-ray light curves, in which three of them are reported for the first time. Furthermore, intraday gamma-ray variations are detected from NVSS J053954-283956 and NVSS J080518+ 614423. The doubling variability timescale of the former source is limited as short as less than or similar to 1 hr (at the source frame). Together with variability amplitude over one order of magnitude, NVSS J053954-283956 is the most distant gamma-ray flaring blazar so far. Meanwhile, intraday optical variability of NVSS J163547+ 362930 is found based on an archival PTF/iPTF light curve. Benefiting from the multi-wavelength activity of these sources, constraints on their Doppler factors, as well as the locations of the gamma-ray radiation region and indications for the SDSS high redshift jetted active galactic nuclei deficit are discussed.