Optical Variability Properties of Southern TESS Blazars

TL;DR

This study analyzes optical light curves of 67 southern blazars from TESS, revealing variability characteristics, power spectral properties, and timescales, with implications for jet-originated optical variability.

Contribution

It provides the first detailed power spectral density analysis of southern blazars using TESS data, identifying characteristic timescales and variability patterns.

Findings

Only 15 BLLs and 18 FSRQs show significant variability.

Power spectral slopes around 2 with some breaks indicate jet-related variability.

Characteristic timescales range from ~0.8 to 8 days.

Abstract

We present a study of high-cadence, high-precision, optical light curves from the TESS satellite of 67 blazars in the southern sky. We provide descriptive flux statistics, power spectral density model parameters, and characteristic variability timescales. We find that only 15 BL Lacertae objects (BLLs) and 18 Flat Spectrum Radio Quasars (FSRQs) from the initial 26 and 41, respectively exhibit statistically-significant variability. We employ an adapted Power Spectral Response method to test the goodness of fit for the power spectral density function (PSD) to 3 power-law variant models. From our best-fitting description of the PSD, we extract the high-frequency power-spectral slopes and, if present, determine the significant bend or break in the model to identify characteristic timescales. We find no significant difference in the excess variance or rms-scatter between blazar subpopulations. We identify a linear rms-flux relation in ~69% of our sample, in which ~20% show a strong correlation. We find that both subpopulations of blazars show power spectral slope of $\alpha$~2 in which a broken power-law best fits 5 BLL & 6 FSRQ and a bending power-law best fits 1 BLL & 5 FSRQ. The shortest timescales of variability in each light curve range widely from minutes to weeks. Additionally, the objects' characteristic timescales range from ~0.8-8 days, consistent with the optical variability originating in the jet.