Flare genesis in relativistic jet: Disentangling the drivers of variability in the blazar 4C +27.50

Abstract

Recently, blazar 4C +27.50 was found to be flaring in gamma-rays since its detection with Fermi-LAT in 2008. For the first time, a dedicated temporal and spectral study of the blazar 4C +27.50 has been performed in this work to understand the nature of this object. We used the Bayesian block algorithm to identify four flaring states and one quiet state in the 2-year-long Fermi-LAT light curve. Simultaneous broadband flaring episodes have been observed, and a significant correlation is seen between optical and $\gamma$-ray emission, suggesting the co-spatial origin of the broadband emission. The variation of fractional variability amplitude with respect to frequency shows a nearly double hump structure similar to broadband SED. The fastest flux doubling time in the 1-day binned $\gamma$-ray light curve is found to be about 7.8 hours. A curvature in $\gamma$-ray spectra has been observed, possibly caused by a stochastic particle acceleration process rather than radiative cooling. No evident correlation was found in the $\gamma$-ray flux-index plot, but a clear harder-when-brighter trend is observed in the X-ray flux-index plot. A one-zone leptonic model has been implemented to understand broadband emission during the quiet and flaring states, and the variation of the jet parameters is been investigated. A gradual increment in BLR and Disk energy density has been observed from a quiet to the flaring state. Broadband SED modeling suggested that an enhancement in the magnetic field, particle energy, and bulk Lorentz factor might have caused the flaring events.