Possible Quasi-periodic Oscillation in the Distant γ-Ray Blazar PKS 0454–234

Document Type : Original Article


1 Physics Department, Faculty of Science, Tanta University, Tanta 31527, Egypt

2 Basic Science Department, Modern Academy for Engineering and Technology, Maadi 11585, Cairo, Egypt.

3 Physics Department, Faculty of Science, Tanta University, Tanta 31527, Tanta, Egypt.

4 Centre for Theoretical Physics, The British University in Egypt, Sherouk City 11837, Cairo, Egypt.


An important observational feature of Fermi-LAT blazars is their variability, which remarkably occasionally shows quasi-periodic oscillations (QPOs); a characteristic that could convey information regarding the emission mechanism from their central engines, as well as the possibility of observing merging systems. This work searches for 0.1–100 GeV γ-ray periodic modulations in the distant (redshift=1.003) flat-spectrum radio quasar PKS 0454–234, using the Fermi-LAT pass 8 data for time span of about 14 yr. The search for such signals in the γ-ray light curves was carried out using four methods: the Generalized Lomb-Scargle periodogram (GLSP), the weighted wavelet z-transform (WWZ), the REDFIT algorithm, as well as the auto-correlation function. Two possible QPO signals were found with periods of 3.51±0.33 yr and 6.10±0.82 yr, at the significance levels of ~4σ and ~3σ, respectively. Even though the latter periodicity is less significant than the former, it in fact gives a better fit to the fluxes. Considering a super binary black hole system (SBBHS) model, the parameters of the binary were estimated (for the period of 6 yr) as follows: a binary separation of R∼0.005 pc, with total mass M∼4.69×10^8 M⊙, and decay time of the gravitational wave emission T(GW)∼9.56×10^4 yr.