2022MNRAS.513.2239P

Blazars are a class of AGN, one of their jets is pointed towards the earth. Here, we report about the multiwavelength study for blazar S5 1803+78 between MJD 58727 and MJD 59419. We analysed gamma-ray data collected by Fermi-LAT, X-ray data collected by Swift-XRT & NuSTAR, and optical photons detected by Swift-UVOT & TUBITAK observatory in Turkey. Three flaring states are identified by analysing the gamma-ray light curve. A day-scale variability is observed throughout the flares with the similar rise and decay times suggesting a compact emission region located close to the central engine. Cross-correlation studies are carried out between gamma-ray, radio, and X-ray bands, and no significant correlation is detected. The gamma-ray and optical emission are significantly correlated with zero time lag suggesting a co-spatial origin of them. The broad-band spectral energy distribution (SED) modelling was performed for all the flaring episodes as well as for one quiescent state for comparison. SEDs are best fitted with the synchrotron-self Compton (SSC) model under a one-zone leptonic scenario. The SED modelling shows that to explain the high flaring state, strong Doppler boosting is required.