The June 2016 Optical and Gamma-Ray Outburst and Optical Micro-Variability of the Blazar 3C454.3

Abstract

The quasar 3C454.3 underwent a uniquely-structured multi-frequency outburst in June 2016. The blazar was observed in the optical $R$ band by several ground-based telescopes in photometric and polarimetric modes, at $\gamma$-ray frequencies by the \emph{Fermi}\ Large Area Telescope, and at 43 GHz with the Very Long Baseline Array. The maximum flux density was observed on 2016 June 24 at both optical and $\gamma$-ray frequencies, reaching $S_{\mathrm{opt}}^{\max }=18.91\pm 0.08$ mJy and $S_{\gamma }^{\max }=22.20\pm 0.18\times 10^{-6}$ ph cm${}^{-2}$ s${}^{-1}$, respectively. The June 2016 outburst possessed a precipitous decay at both $\gamma$-ray and optical frequencies, with the source decreasing in flux density by a factor of 4 over a 24-hour period in $R$ band. Intraday variability was observed throughout the outburst, with flux density changes between 1 and 5 mJy over the course of a night. The precipitous decay featured statistically significant quasi-periodic micro-variability oscillations with an amplitude of $\sim 2$-$3\%$ about the mean trend and a characteristic period of 36 minutes. The optical degree of polarization jumped from $\sim 3\%$ to nearly 20\% during the outburst, while the position angle varied by $\sim120\degr$. A knot was ejected from the 43 GHz core on 2016 Feb 25, moving at an apparent speed $v_{\mathrm{app}}=20.3c\pm 0.8c$. From the observed minimum timescale of variability ${\tau }_{\mathrm{opt}}^{\min }\approx 2$ hr and derived Doppler factor $\delta =22.6$, we find a size of the emission region $r\lesssim 2.6\times 10^{15}$ cm. If the quasi-periodic micro-variability oscillations are caused by periodic variations of the Doppler factor of emission from a turbulent vortex, we derive a rotational speed of the vortex $\sim 0.2c$.

19 pages, 13 figures, 3 tables, accepted to the Astrophysical Journal 2019 March 9

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Cited by in corpus (10)

• Kinematics of Parsec-Scale Jets of Gamma-Ray Bright Blazars at 43 GHz during Ten Years of the VLBA-BU-BLAZAR Program
• A comprehensive power spectral density analysis of astronomical time series I: the Fermi-LAT gamma-ray light curves of selected blazars
• Two Flares with One Shock: the Interesting Case of 3C 454.3
• Gamma-Ray Flares in Long Term Light Curve of 3C 454.3
• 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
• Optical variability of the blazar 3C 371: from minute to year timescales
• On the origin of GeV spectral break for Fermi blazars: 3C 454.3
• Emission Line Variability during a Nonthermal Outburst in the Gamma-Ray Bright Quasar 1156+295
• Revisiting radio variability of the blazar 3C 454.3
• Relationship between the $\gamma -$ray variability and the pc-scale jet in the blazar 3C 454.3