SIMBAD references

Variability is a typical observation feature of Fermi blazars, which sometimes shows quasi-periodic oscillation (QPO). In this work, we obtain 5 day binned light curves (with a time coverage of ∼12.9 yr) for S5 1044+71, based on Fermi-LAT data; apply five different methods-Date-compensated Discrete Fourier Transform, Jurkevich, Lomb-Scargle Periodogram, a Fortran 90 program, and the Weighted Wavelet Z-transform-to the γ-ray light curve; and find a possible QPO of 3.06 ± 0.43 yr at the significance level of ∼3.6σ. A binary black hole model, including an accretion model and a dual-jet model, is used to explain this quasi-periodic variability. We also estimate the Doppler factors and the apparent velocity for the two jet components. We speculate that this γ-ray quasi-periodic modulation suggests the presence of a binary supermassive black hole in S5 1044+71.