Constraining the Location of the γ-Ray Emission Region in Radio-loud AGN 3C 380

Abstract A detailed broadband spectral and temporal study of a radio-loud active galactic nucleus, 3C 380, is carried out using 14.5 yr of Fermi-LAT data, available Swift observations, and data from other observatories, including AstroSat (2020 August). The source exhibited a GeV outburst on 2020 September 5. Given the sparsity of Swift observations, no useful correlations could be established between γ -ray, X-ray, and UV/optical bands. The source is also a part of the Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments survey and has been monitored at 15 GHz for over a decade. The correlation studies show that radio emission lags γ -rays by ∼150 days. We constrain the location of γ -ray emission by the core shift measurements from the literature and the observed time delays. Using this localization, we constructed and modeled the broadband spectral energy distribution (SED) of the source during its high γ -ray activity states and for the long-term averaged state. The SEDs during the high γ -ray activity states are modeled with two zones: one corresponding to the “steady” or the emission from the source averaged over more than a decade and another corresponding to the “flare” emission. We conclude that the high-energy emission originates within the parsec-scale jet, and moving shocks in the region drive the observed γ -flux variations.