Optical multi-color monitoring of the BL Lacertae Object S5 0716+714 with BOOTES-4

Abstract

S5 0716+714 had been monitored from November, 2017 to May, 2018 with the 60 cm autonomous telescope BOOTES-4 (the fourth station of the BOOTES network), which located at the Lijiang Observatory of the Yunnan Observatories, the Chinese Academy of Sciences. The observations include 125 nights. The time span per night is from 0.026 hours to 10.73 hours (average time span 3.94 hours). The time intervals between two adjacent bands are about 2.23 minutes. With the high quality data, we use one-way analysis of variance (ANOVA) and $F$ -test to check the intraday flux variability (IDV) by considering the 62 nights with time span more than 4 hours. The values of duty cycle (DC) are 77%, 83%, 74% for $g$ , $r$ , $i$ bands respectively. The intraday flux variability amplitude distributions are from 2.54% to 35.35% and the mean value is 16.33%. The analysis of z-transformed discrete correlation function (ZDCF) shows that the significant time lags between different wavebands are not found. The scope of characteristic flux variability timescales is from 0.015 day to 0.164 day, and the mean value is 0.066 day. Most of nights show bluer when brighter (BWB) trends while some nights have weak BWB trends or redder-when brighter (RWB) trends in different brightness. The shock-in-jet model and multiple variation components in the jet could explain the IDV and color behaviors.