Possible quasi-periodic oscillation in the distant γ-ray blazar PKS 0454-234

Abstract EN

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 × 108 M⊙, and decay time of the gravitational wave emission TGW ∼ 9.56 × 104 yr.