Probable Quasi-Periodic Oscillations in the TESS observations of blazars in the Swift X-ray Survey

This work presents possible quasi-periodic oscillations in the Transiting Exoplanet Survey Satellite observations of blazars that are in the 157-month hard X-ray survey done by Swift’s Burst Alert Telescope. We report observations from four sources, J1104.4+3812, J1654.0+3946, J0353.4-6830, and J1941.3-6216, that show at least 3σ local significance in generalized Lomb-Scargle periodogram and weighted wavelet Z-transform methods. These results are also checked using a continuous autoregressive moving average analysis that also predicts the absent data tentatively using stochastic differential equations. Each of these four sources exhibits a nominal QPO signal frequency in the range of 0.5–1.1 d−1, resulting in at least 5 putative cycles. However, when the number of frequencies examined and the number of sources examined are both taken into account, the global significances are reduced to ≈2.2σ for J1654.0+3964 (Mrk 501), and to ≈1.9σ for other sources. These QPOs are thought to arise from the processes within the relativistic jet. Plausible explanations include the kink instability, which arises due to current-driven instabilities in the plasma or the precession of substructures, or mini-jets, within the jets.