Intra-day variability of BL Lacertae from 2016 to 2018

TL;DR

This study monitored BL Lacertae over two years, revealing significant intraday variability, a bluer-when-brighter trend, and correlated wavelength variations with no time lag, enhancing understanding of its short-term behavior.

Contribution

First detailed multi-band intra-day variability analysis of BL Lacertae over a two-year period, identifying color-magnitude behavior and wavelength correlation.

Findings

Significant intraday variability on 12 out of 14 nights

Bluer-when-brighter chromatism observed

No inter-band time lag detected

Abstract

We monitored BL Lacertae in the B, V, R and I bands for 14 nights during the period of 2016-2018. The source showed significant intraday variability on 12 nights. We performed colour-magnitude analysis and found that the source exhibited bluer-when-brighter chromatism. This bluer-when-brighter behavior is at least partly caused by the larger variation amplitude at shorter wavelength. The variations at different wavelengths are well correlated and show no inter-band time lag.