A 31.3 day Transient Quasiperiodic Oscillation in Gamma-ray Emission from Blazar S5 0716+714

TL;DR

This paper reports the discovery of a transient 31.3-day quasiperiodic oscillation in the gamma-ray emission of blazar S5 0716+714, using advanced time-series analysis and statistical validation.

Contribution

It is the first detection of a month-scale transient QPO in gamma-ray blazar emission with detailed statistical significance assessment.

Findings

Detected a 31.3-day QPO with ~4.1σ confidence level.

The QPO is transient, observed over seven cycles.

Helical jet and blob motion models explain the QPO.

Abstract

We systematically search for quasiperiodic oscillatory (QPO) signals on the month timescale among the 1525 sources given in the Fermi Large Area Telescope Light Curve Repository. We find a transient QPO of 31.3$\pm$1.8 days in the gamma-ray band light curve of the TeV blazar S5 0716+714, which has seven cycles (MJD 55918-56137) for the first time by weighted wavelet Z-transform and Lomb-Scargle periodogram methods. Monte Carlo simulations based on the power spectral density and probability distribution function were used to evaluate the confidence level of the QPO, and the result is $\sim 4.1\sigma$. Seasonal autoregressive integrated moving average modeling of the light curve revealed it is a significant physical QPO. The physical models to explain the sporadic QPO of the month-timescale QPOs in blazar were discussed. Our studies indicate that the helical jet model and blob move helically in a curved jet model to properly explain this kind of transient QPO.