Simultaneous B'V'R' Monitoring of BL Lacertae Object S5~0716+714 and Detection of Inter-Band Time Delay

TL;DR

This study conducted simultaneous optical monitoring of the BL Lac object S5 0716+714 at three wavelengths, revealing intranight variations, bluer-when-brighter chromatism, and inter-band time delays, enhancing understanding of its variability behavior.

Contribution

First simultaneous multi-band optical monitoring of S5 0716+714 with a novel system, detecting inter-band time delays and chromatic variations.

Findings

Intranight variations observed on four nights.

Bluer-when-brighter chromatism detected.

Inter-band time delay of about 30 minutes between B'/V' and R' bands.

Abstract

We present the results of our optical monitoring of the BL Lac object S5 0716+714 on seven nights in 2006 December. The monitoring was carried out simultaneously at three optical wavelengths with a novel photometric system. The object did not show large-amplitude internight variations during this period. Intranight variations were observed on four nights and probably on one more. Strong bluer-when-brighter chromatism was detected on both intranight and internight timescales. The intranight variation amplitude decreases in the wavelength sequence of B', R', and V'. Cross correlation analyses revealed that the variability at the $B'$ and $V'$ bands lead that at the $R'$ band by about 30 minutes on one night.