SIMBAD references

We present a detailed temporal and spectral study of the blazar 3C 279 using multiwavelength observations from Swift-XRT, Swift-UVOT, and Fermi-LAT during a flare in 2018 January. The temporal analysis of γ-ray light curve indicates a lag of ∼1 d between the 0.1-3 GeV and 3-500 GeV emission. Additionally, the γ-ray light curve shows asymmetry with slow rise-fast decay in energy band 0.1-3 GeV and fast rise-slow decay in the 3-500 GeV band. We interpret this asymmetry as a result of shift in the Compton spectral peak. This inference is further supported by the correlation studies between the flux and the parameters of the log-parabola fit to the source spectra in the energy range 0.1-500 GeV. We found that the flux correlates well with the peak spectral energy and the log-parabola fit parameters show a hard index with large curvature at high flux states. Interestingly, the hardest index with large curvature was synchronous with a very high energy flare detected by H.E.S.S. Our study of the spectral behaviour of the source suggests that γ-ray emission is most likely to be associated with the Compton upscattering of IR photons from the dusty environment. Moreover, the fit parameters indicate the increase in bulk Lorentz factor of emission region to be a dominant cause for the flux enhancement.