Multi-wavelength search for quasi-periodic oscillations in BL Lac 4FGL J0112.1+2245.

We have assembled historical light curve data of the BL Lac object 4FGL J0112.1+2245 at radio, optical and γ -ray bands, spanning about a 12.5, 8.4, and 11.9 yr period, respectively. We used the Lomb-Scargle Periodogram (LSP), Weighted Wavelet Z-transform (WWZ) and epoch folding methods to search for periodicity in the light curves. The results indicate that there is a possible quasi-periodic oscillation (QPO) of 896 ± 32 days for γ -rays, 880 ± 54 days in the optical, and 830 ± 33 days in the radio band, respectively. In addition, the QPO signals evaluated by employing a red noise model were found to be above 3 σ (99.7%) in the three bands. Assuming that it originates from a jet in helical motion in a supermassive binary black hole system undergoing a merger, we estimate the primary black hole mass M ≃ 2.2 × 10 9 M ⊙ . Using the discrete correlation function (DCF) method, we investigated the correlation among multi-wavelength bands, and found that there is a significant correlation between the different bands from MJD 57670 to 59000. The results indicated that the optical flux in this source is originating from the same or vicinal emission region as the γ -ray and show a time lag of 73 days with radio band. Across the data as a whole, the DCF results show that the optical correlation with radio and γ -ray is significant, while the correlation between the γ -ray and radio bands are weak. [ABSTRACT FROM AUTHOR]