Multicolour Optical Variability Monitoring of Blazars with High Time Resolution

TL;DR

This study presents high time-resolution, multicolour optical observations of eight gamma-ray blazars, revealing intraday variability, chromatic trends, potential quasi-periodic oscillations, and estimating black hole masses.

Contribution

It provides the first detailed multicolour variability analysis of these blazars, identifying QPOs and chromatic trends across different timescales.

Findings

Intraday variability detected in all sources.

Bluer-when-brighter trend observed on intraday timescales.

Potential quasi-periodic oscillation identified in 1ES 1426+42.8.

Abstract

We carried out a high time-resolution, multicolour optical observing campaign for eight $\gamma$-ray detected blazars during 2010-2020. We analyze flux variations, correlations between magnitudes and colours on different timescales. Intraday variability (IDV) is detected in all eight sources of our sample. A bluer-when-brighter (BWB) chromatic trend is dominant on intraday timescales. On the short timescales, the BWB trend only shows up in ON 231, 3C 279, BL Lacertae and 1E 1458.8+2249. There is a BWB trend in 3C 279 on the long timescale. We estimate the upper limits of black hole mass for three blazars (i.e. ON 321, 1ES 1426+42.8, PKS 1510-089) using variability timescales. On April 13, 2010 a potential quasi-periodic oscillation (QPO) with the period of $P=48.67\pm13.90$ minutes is found in 1ES 1426+42.8. The light curve on March 16, 2021 further shows the existence of the QPO phenomenon. The QPO in this target deserves further observation and confirmation.