Detection of quasiperiodic oscillations in the blazar PKS 0735+178 with TESS

Abstract

We report here the detection of signatures of a quasiperiodic oscillation (QPO) and a short flare in the optical light curve of the blazar PKS 0735+178, observed in two sectors, 71 and 72, spanning around 49 d with the Transiting Exoplanet Survey Satellite. The modest flare in sector 71 lasted ∼ 4.3 d and appears as a combination of two sub-flares. In sector 72, a transient QPO with a period ∼ 11.2 h is detected at local and globalsignificance levels of 4.11σ and 3.06σ, respectively. We used weighted wavelet z transform, Lomb–Scargle periodogram, and phase dispersion minimization analysis techniques to look for and confirm the QPO feature. We also performed a segment-wise statistical inspection of these light curves and discuss here possible mechanisms that could explain the observed flux behaviour.