To get insights into its dominant emission mechanisms, we generated the optical spectral energy distributions of the source on 79 nights and estimated the spectral indices by fitting a simple power law. From correlation analysis, we observed that the emission in all optical bands were strongly correlated with a time lag of ∼0 days. However, no such variability was detected during the flaring period.
![vani rani today episode 1093 vani rani today episode 1093](https://i.ytimg.com/vi/g9Zp1bVbHyE/maxresdefault.jpg)
We found significant variability in 2 of these 13 nights. On 13 nights, covering both flaring and nonflaring periods, we searched for intraday variability using the power-enhanced F -test and the nested ANOVA test. We also found the source in its brightest ( R mag = 13.617) and faintest ( R mag = 15.888) states to date. Our observing campaign detected a historically bright optical flare during MJD 59,063.5−MJD 59,120.5. We report the results from our study of the blazar S5 1803+784 carried out using quasi-simultaneous B, V, R, and I observations from 2020 May to 2021 July on 122 nights. However, the long-term flux and colour variability of BL Lac suggests that these can arise from modest changes in velocities or viewing angle toward the emission region, leading to variations in the Doppler boosting of the radiation by a factor of ∼1.2 over the period of these observations. The nature of the long-term variability of 3C 66A and S4 0954+658 is consistent with a model of a non-thermal variable component that has a continuous injection of relativistic electrons with power-law distributions around 4.3 and 4.6, respectively. The colour variations are mildly chromatic on long time-scales for two of them. All three TeV blazars exhibited strong flux variability during our observations. We also examine the optical spectral energy distributions of these blazars, which are crucial in understanding the emission mechanism of long-term variability in blazars. We study flux and spectral variability of these blazars on these lengthy time-scales. Our extensive observations were performed in a total of 360 nights which produced ∼6820 image frames in BVRI bands. We present the results of photometric observations of three TeV blazars, 3C 66A, S4 0954+658, and BL Lacertae (BL Lac), during the period 2013–2017. We also discuss possible physical causes of the observed spectral variability. Target using the B, V, R, and I data sets for all 13 nights which could help us investigate the physical process responsible for the observed variations We also generated spectral energy distribution of the Using discrete correlation technique, we found that intraday light curves in both V and R filters are almost consistent and well correlated with each other. From the colour–magnitude analysis of the source, we found that the spectra of the target get flatter as it becomesīrighter on intranight time-scale.
![vani rani today episode 1093 vani rani today episode 1093](http://ndtvimages.yuppcdn.net/images/Sun_TV_Vani_Rani_656.jpg)
On three nights in V and R filters while displayed hints of variability on six other dates in R passband and on two nights in V filter. Source was found to be active during the whole monitoring period and showed significant intraday variability We have studied multiband optical flux variations, colour variation and spectralĬhanges in this blazar. We monitored BL Lacertae for 13 nights in optical B, V, R, and I bands during 2014 October and November including quasi-simultaneous observations in V and R bands using two optical telescopes in India.