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We detected a possible quasi-periodic oscillation (QPO) of ~ 71 days in the 0.1 -- 300 GeV gamma-ray Fermi-LAT light curve of the high redshift flat spectrum radio quasar B2 1520+31. We identify and confirm that quasi-period by Lomb Scargle periodogram (LSP), and weighted wavelet z-transform (WWZ) analyses. Using this QPO period, and assuming it originates from accretion-disc fluctuations at the innermost stable circular orbit, we estimate the central supermassive black hole mass to range between ~ 5.4 * 10$^{9}$ M$_{odot}$ for a non-rotating black hole and ~ 6.0 * 10$^{10}$ M$_{odot}$ for a maximally rotating black hole. We briefly discuss other possible radio-loud active galactic nuclei emission models capable of producing a gamma-ray QPO of such a period in a blazar.
We report the detection of a probable $gamma$-ray quasi-periodic oscillation (QPO) of around 314 days in the monthly binned 0.1 -- 300 GeV $gamma$-ray {it Fermi}-LAT light curve of the well known BL Lac blazar OJ 287. To identify and quantify the QPO
The OVRO 40-m telescope has been monitoring the 15 GHz radio flux density of over 1200 blazars since 2008. The 15 GHz light curve of the flat spectrum radio quasar J1359+4011 shows a strong and persistent quasi-periodic oscillation. The time-scale of
High-redshift ($z>2$) blazars are the most powerful members of the blazar family. Yet, only a handful of them have both X-ray and $gamma$-ray detection, thereby making it difficult to characterize the energetics of the most luminous jets. Here, we re
Long-term gamma-ray variability of a non-blazar Active Galactic Nucleus (AGN) PKS 0521-36 is investigated by using Fermi-LAT pass 8 data covering from 2008 August to 2021 March. The results show that the histogram of the gamma-ray fluxes follows a lo
We report on quasi-periodic variability found in two blazars included in the Steward Observatory Blazar Monitoring data sample: the BL Lac object 3C 66A and the Flat Spectrum Radio Quasar B2 1633+38. We collect optical photometric and polarimetric da