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

Abstract

Over the years, the flat-spectrum radio quasar 3C 454.3 has presented phases of very high activity (flares) in which the different wave bands increase their flux dramatically. In this work, we perform multiwavelength analysis from radio to gamma-rays and study the Mg ii λ2798 emission line and the UV Fe ii band from 2008 to 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 ∼4.6 pc from the radio core). The different behavior of the spectral index in the first (5000 < JD − 2,450,000 < 5600) and second (6600 < JD − 2,450,000 < 7900) flaring periods suggests 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 line has an anticorrelation with the UV continuum while Fe ii correlates positively, except at 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 region emitting seed photons is co-spatial with that emitting gamma-rays. However, a study of the spectral energy distribution using a multizone jet emission model is required to confirm the nature of each significant flare during the second period.

Correlation between optical flux and polarization variations in Flat Spectrum Radio Quasars on diverse timescales

“…The optical and 𝛾−ray flux variations of 3C 454.3 were found to be well correlated with zero time delay (e.g. Ramakrishnan et al 2015;Amaya-Almazán et al 2021).…”

“…However, some recent studies have also reported temporary SSC dominance on some FSRQs (e.g. Patiño-Álvarez et al 2018Patiño-Álvarez et al , 2019Chavushyan et al 2020;Amaya-Almazán et al 2021).…”

“…Changes in the observed polarization position angle could be related to changes in the direction of the magnetic field in the jet along the observer's line of sight. Moreover, as the flux variations in the optical and GeV 𝛾-rays are connected (Bonning et al 2009;Chatterjee et al 2012;Liao et al 2014;Carnerero et al 2015;Patiño-Álvarez et al 2018;Chavushyan et al 2020;Amaya-Almazán et al 2021, however, see also Rajput et al (2019Rajput et al ( , 2020a and references therein for no correlation between optical and 𝛾-ray flux variations) flux and polarization variability observations at different wavelengths can provide important inputs on the connection between different emission regions in the jets of these sources. Also, observations with the Fermi Gamma-ray Space Telescope (hereinafter Fermi) have revealed a close association between the 𝛾-ray flare and the rotation of the optical polarization position angle, which again can constrain the nature of the high energy 𝛾-ray emission process (Marscher et al 2008;Abdo et al 2010a;Marscher et al 2010).…”

Modeling the Broadband Emission of 3C 454.3

“…1 suggests that the flares in different bands are nearly correlated or appear with small legs. A cross correlation analysis of the 3C 454.3 emission in different bands has been performed in Amaya-Almazán et al (2021) where a detailed comparison of the emission in various bands is provided (see Table 2 and 3 The flux in units of 10 −6 photon cm −2 s −1 .…”

“…This source was extensively studied in the multiwavelength band over the last two decades (e.g., Giommi et al 2006). However, after the prominent optical outburst in 2005 with a peak optical brightness of 𝑅 = 12 mag, the source remained active showing several bright flares, it has become a target of multiwavelength studies (Raiteri et al 2008(Raiteri et al , 2011Pacciani et al 2010;Abdo et al 2011Abdo et al , 2009Ackermann et al 2010;Jorstad et al 2013;Amaya-Almazán et al 2021). This multiwavelength campaigns provided unprecedented information on this source.…”