Multiwavelength analysis and the difference in the behavior of the spectral features during the 2010 and 2014 flaring periods of the blazar 3C 454.3

TL;DR

This study analyzes multiwavelength data of blazar 3C 454.3 from 2008 to 2018, revealing different spectral behaviors during two major flaring periods and suggesting changes in emission mechanisms and physical conditions.

Contribution

It provides a detailed comparison of spectral feature behavior during two flaring periods, highlighting the complex nature of emission regions and mechanisms in blazar 3C 454.3.

Findings

Correlation between radio flux and superluminal blob ejection.

Different spectral index behaviors in two flaring periods.

Mg II anti-correlates with UV continuum, Fe II correlates positively.

Abstract

The flat-spectrum radio quasar 3C~454.3 throughout the years has presented very high activity phases (flares) in which the different wavebands increase their flux dramatically. In this work, we perform multiwavelength analysis from radio to gamma-rays and study the Mg~II~$\lambda 2798$\AA\ emission line and the UV~Fe~II band from 2008-2018. We found that an increase in the 43 GHz flux density of the quasi-stationary component C, coincides with the estimated time at which a superluminal blob ejected from the radio core (which caused the brightest flare of 2010) collides with the quasi-stationary component (at a projected distance of $\sim4.6$ pc from the radio core). The spectral index different behavior in the first ($5000 < \text{JD}-2450000 < 5600$) and second ($6600 < \text{JD}-2450000 < 7900$) flaring periods suggest changes in the physical conditions. The complex nature of the second period can be a result of a superposition of multiple events at different locations. The Mg~II has an anti-correlation with the UV-continuum while Fe~II correlates positively. Except by the time of the brightest flare of 2010, when both have a strong response at high continuum luminosities. Our results suggest that the dominant gamma-ray emission mechanism for the first flaring period is External Compton. For the second flaring period the seed photons emission region is co-spatial with the gamma-ray emission region. However, a SED study using a multizone jet emission model is required to confirm the nature of each significant flare during the second period.