Detection of a Transient Quasiperiodic Oscillation in γ-Rays from Blazar PKS 2255-282

Abstract We conducted a comprehensive variability analysis of the blazar PKS 2255-282 using Fermi-LAT observations spanning over 4 yr, from MJD 57783.5 to 59358.5. Our analysis revealed a transient quasiperiodic oscillation (QPO) with a period of 93 ± 2.6 days. We employed a variety of Fourier-based methods, including the Lomb–Scargle periodogram (LSP) and weighted wavelet Z-transform (WWZ), as well as time domain analysis techniques such as seasonal and nonseasonal autoregressive Integrated moving average models and the Stochastic modeling with stochastically driven damped harmonic oscillator models. Consistently, the QPO with a period of 93 days was detected across all methods used. The observed peak in LSP and time-averaged WWZ plots has a significance level of 4.06 σ and 3.96 σ , respectively. To understand the source of flux modulations in the light curve, we explored various physical models. A plausible scenario involves the precession of the jet with a high Lorentz factor or the movement of a plasma blob along a helical trajectory within the relativistic jet.