Two repeated quasi-periodic oscillations in the FSRQ S5 1044+71 observed by TESS

TL;DR

This study reports the first detection of two repeated quasi-periodic oscillations in the FSRQ S5 1044+71 using TESS data, suggesting possible origins in jet instability or accretion disk hot spots, and estimating the black hole mass.

Contribution

First identification of repeated QPOs in S5 1044+71, with analysis of their potential origins and black hole mass estimation.

Findings

Detected QPOs of ~7.0 and ~7.3 days with >3.5σ significance.

QPOs likely originate from jet kink instability or accretion disk hot spots.

Estimated black hole mass of 3.49 x 10^9 solar masses.

Abstract

In this work, we report for the first time two repeated quasi-periodic oscillations (QPOs) in the light curve of the Flat Spectrum Radio Quasar (FSRQ) S5 1044+71. This source was observed by the Transiting Exoplanet Survey Satellite (TESS) in multiple sectors. We used the generalized Lomb-Scargle periodogram method and weighted wavelet Z-transform method to search for significant periodic signals. The main results are as follows: We found QPOs of $\sim$ 7.0 days (persisted for 4 cycles, with a significance of $\sim3.5\sigma$) and $\sim$ 7.3 days (persisted for 5 cycles, with a significance of $\sim3.8\sigma$) in the light curves of Sector 47 and EP1, respectively. Considering range of error, we consider them to be the same. We discussed two likely models of these rapid quasi-periodic variations: One comes from the jet and the other from the accretion disk. For the first one, we consider kink instability of the jet as a plausible explanation. Second, the QPO is probable to come from the main hot spots in the accretion disk, which is located approximately within the innermost stable circular orbit allowed by general relativity. Based on this model, we estimate the mass of the black hole in S5 1044+71 to be $3.49 \times 10^9 M_{\odot}$.