Broadband Variability and Correlation Study of 3C 279 during Flares of 2017–2018

Abstract

A multiwavelength temporal and spectral analysis of flares of 3C 279 during 2017 November–2018 July are presented in this work. Three bright gamma-ray flares were observed simultaneously in X-ray and optical/UV along with a prolonged quiescent state. A “harder-when-brighter” trend is observed in both gamma-rays and X-rays during the flaring period. The gamma-ray light curve for all the flares is binned in one day time bins and a day-scale variability is observed. Variability time constrains the size and location of the emission region to 2.1 × 10 16 cm and 4.4 × 10 17 cm, respectively. The fractional variability reveals that the source is more than 100% variable in gamma-rays and it decreases toward the lower energy. A cross-correlation study of the emission from different wavebands is done using the discrete correlations function method, which shows a strong correlation between them without any time lags. The zero time lag between different wavebands suggests their cospatial origin. This is the first time 3C 279 has shown a strong correlation between gamma-ray and X-ray emission with zero time lag. A single-zone emission model was adopted to model the multiwavelength spectral energy distributions by using the publicly available code GAMERA. The study reveals that a higher jet power in electrons is required to explain the gamma-ray flux during the flaring state, as much as 10 times that required for the quiescent state. However, more jet power in the magnetic field has been observed during the quiescent state compared to the flaring state.