PREPRINT

# A 31.3 day transient quasi-periodic oscillation in gamma-ray emission from the blazar S5 0716+714

Junping Chen, Tingfeng Yi, Yunlu Gong, Xing Yang, Zhihui Chen, Xin Chang, Lisheng Mao

Submitted on 14 September 2022

## Abstract

We systematically search for quasi-periodic oscillatory (QPO) signals on the monthly time scale among the 1525 sources given in the Fermi Large Area Telescope Light Curve Repository (LCR). We find a transient QPO of 31.3$±$1.8 days in the gamma-ray band light curve of the TeV blazar S5 0716+714, which has 7 cycles (MJD 55918-56137) for the first time by Weighted wavelet Z-transform (WWZ) and Lomb-Scargle periodogram (LSP) methods. Monte Carlo simulations based on power spectral density (PSD) and probability distribution function (PDF) were used to evaluate the confidence level of the QPO, and the result is $\sim 4.1\sigma$. Seasonal Autoregressive Integrated Moving Average (SARIMA) modeling of the light curve revealed it is a significant physical QPO. the physical models to explain the sporadic QPO of the month time scale 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.

## Preprint

Comment: 13 pages, 5 figures, accepted for publication in ApJ

Subjects: Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Astrophysics of Galaxies