|Authors : ||Abhradeep Roy (1), Arkadipta Sarkar (1), Anshu Chatterjee (1), Alok C. Gupta (2), Varsha R. Chitnis (1), Paul J. Wiita (3).
(1) Department of High Energy Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai, India,
(2) Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, India,
(3) Department of Physics, The College of New Jersey, Ewing, NJ, USA.|
|Abstract : ||We present periodicity search analyses on the gamma-ray lightcurve of the TeV blazar PKS 1510-089 observed by the Fermi Large Area Telescope. We report the detection of two transient quasi-periodic oscillations: a 3.6-day QPO during the outburst in 2009 that lasted five cycles (MJD 54906--54923); and a periodicity of 92 days spanning over 650 days from 2018 to 2020 (MJD 58200--58850), which lasted for seven cycles. We employed the Lomb-Scargle periodogram, Weighted Wavelet Z-transform, REDFIT, and the Monte Carlo lightcurve simulation techniques to find any periodicity and the corresponding significance. The 3.6-day QPO was detected at a moderate significance of ∼3.5 sigmas, while the detection significance of the 92-day QPO was ∼7.0 sigmas. We explore a few physical models for such transient QPOs including a binary black hole system, precession of the jet, a non-axisymmetric instability rotating around the central black hole near the innermost stable circular orbit, the presence of quasi-equidistant magnetic islands inside the jet, and a geometric model involving a plasma blob moving helically inside a curved jet. |