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Register a new userA peculiar multi-wavelength flare in the Blazar 3C 454.3
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The blazar 3C454.3 exhibited a strong flare seen in gamma-rays, X-rays, and optical/NIR bands during 3--12 December 2009. Emission in the V and J bands rose more gradually than did the gamma-rays and soft X-rays, though all peaked at nearly the same time. Optical polarization measurements showed dramatic changes during the flare, with a strong anti-correlation between optical flux and degree of polarization (which rose from ~ 3% to ~ 20%) during the declining phase of the flare. The flare was accompanied by large rapid swings in polarization angle of ~ 170 degree. This combination of behaviors appear to be unique. We have cm-band radio data during the same period but they show no correlation with variations at higher frequencies. Such peculiar behavior may be explained using jet models incorporating fully relativistic effects with a dominant source region moving along a helical path or by a shock-in-jet model incorporating three-dimensional radiation transfer if there is a dominant helical magnetic field. We find that spectral energy distributions at different times during the flare can be fit using modified one-zone models where only the magnetic field strength and particle break frequencies and normalizations need change. An optical spectrum taken at nearly the same time provides an estimate for the central black hole mass of ~ 2.3 * 10^9 M_sun. We also consider two weaker flares seen during the $sim 200$ d span over which multi-band data are available. In one of them, the V and J bands appear to lead the $gamma$-ray and X-ray bands by a few days; in the other, all variations are simultaneous.
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We present a multi-wavelength temporal analysis of the blazar 3C 454.3 during the high $gamma$-ray active period from May-December, 2014. Except for X-rays, the period is well sampled at near-infrared (NIR)-optical by the emph{SMARTS} facility and the source is detected continuously on daily timescale in the emph{Fermi}-LAT $gamma$-ray band. The source exhibits diverse levels of variability with many flaring/active states in the continuously sampled $gamma$-ray light curve which are also reflected in the NIR-optical light curves and the sparsely sampled X-ray light curve by the emph{Swift}-XRT. Multi-band correlation analysis of this continuous segment during different activity periods shows a change of state from no lags between IR and $gamma$-ray, optical and $gamma$-ray, and IR and optical to a state where $gamma$-ray lags the IR/optical by $sim$3 days. The results are consistent with the previous studies of the same during various $gamma$-ray flaring and active episodes of the source. This consistency, in turn, suggests an extended localized emission region with almost similar conditions during various $gamma$-ray activity states. On the other hand, the delay of $gamma$-ray with respect to IR/optical and a trend similar to IR/optical in X-rays along with strong broadband correlations favor magnetic field related origin with X-ray and $gamma$-ray being inverse Comptonized of IR/optical photons and external radiation field, respectively.
We present the gamma-ray data of the extraordinary flaring activity above 100 MeV from the flat spectrum radio quasar 3C 454.3 detected by AGILE during the month of December 2009. 3C 454.3, that has been among the most active blazars of the FSRQ type since 2007, was detected in the gamma-ray range with a progressively rising flux since November 10, 2009. The gamma-ray flux reached a value comparable with that of the Vela pulsar on December 2, 2009. Remarkably, between December 2 and 3, 2009 the source more than doubled its gamma-ray emission and became the brightest gamma-ray source in the sky with a peak flux of F_{gamma,p} = (2000 pm 400) x 10^-8 ph cm^-2 s^-1 for a 1-day integration above 100 MeV. The gamma-ray intensity decreased in the following days with the source flux remaining at large values near F simeq (1000 pm 200) x 10^-8 ph cm^-2 s^-1 for more than a week. This exceptional gamma-ray flare dissipated among the largest ever detected intrinsic radiated power in gamma-rays above 100 MeV (L_{gamma, source, peak} simeq 3 x 10^46 erg s^-1, for a relativistic Doppler factor of {delta} simeq 30). The total isotropic irradiated energy of the month-long episode in the range 100 MeV - 3 GeV is E_{gamma,iso} simeq 10^56 erg. We report the intensity and spectral evolution of the gamma-ray emission across the flaring episode. We briefly discuss the important theoretical implications of our detection.
Opacity-driven shifts of the apparent VLBI core position with frequency (the core shift effect) probe physical conditions in the innermost parts of jets in active galactic nuclei. We present the first detailed investigation of this effect in the brightest gamma-ray blazar 3C454.3 using direct measurements from simultaneous 4.6-43 GHz VLBA observations, and a time lag analysis of 4.8-37 GHz lightcurves from the UMRAO, CrAO, and Metsahovi observations in 2007-2009. The results support the standard Konigl model of jet physics in the VLBI core region. The distance of the core from the jet origin r_c(nu), the core size W(nu), and the lightcurve time lag DT(nu) all depend on the observing frequency nu as r_c(nu)~W(nu)~ DT(nu)~nu^-1/k. The obtained range of k=0.6-0.8 is consistent with the synchrotron self-absorption being the dominating opacity mechanism in the jet. The similar frequency dependence of r_c(nu) and W(nu) suggests that the external pressure gradient does not dictate the jet geometry in the cm-band core region. Assuming equipartition, the magnetic field strength scales with distance r as B = 0.4(r/1pc)^-0.8 G. The total kinetic power of electron/positron jet is about 10^44 ergs/s.
Recent detection of suborbital gamma-ray variability of Flat Spectrum Radio Quasar (FSRQ) 3C 279 by Fermi Large Area Telescope (LAT) is in severe conflict with established models of blazar emission. This paper presents the results of suborbital analysis of the Fermi/LAT data for the brightest gamma-ray flare of another FSRQ blazar 3C 454.3 in November 2010 (MJD 55516-22). Gamma-ray light curves are calculated for characteristic time bin lengths as short as 3 min. The measured variations of the 0.1-10 GeV photon flux are tested against the hypothesis of steady intraorbit flux. In addition, the structure function is calculated for absolute photon flux differences and for their significances. Significant gamma-ray flux variations are measured only over time scales longer than ~5h, which is consistent with the standard blazar models.
In July 2007, the blazar 3C 454.3 underwent a flare in the optical, reaching R~13 on July 19. Then the optical flux decreased by one magnitude, being R~14 when the source was detected by the gamma-ray satellite AGILE, that observed the source on July 24-30. At the same time, the Swift satellite performed a series of snapshots. We can construct the simultaneous spectral energy distribution using optical, UV, X-ray and gamma-ray data. These shows that an increased gamma-ray flux is accompanied by a weaker optical/X-ray flux with respect to the flare observed in the Spring 2005 by INTEGRAL and Swift. This confirms earlier suggestions about the behaviour of the jet of 3C 454.3.
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