Location of the Gamma-Ray Flaring Emission in the Parse-Scale Jet of the BL Lac Object AO 0235+164

International Journal of Modern Physics Conference Series 12/2011; DOI: 10.1142/S2010194512004709
Source: arXiv

ABSTRACT We locate the gamma-ray and lower frequency emission in flares of the BL Lac
object AO 0235+164 at >12pc in the jet of the source from the central engine.
We employ time-dependent multi-spectral-range flux and linear polarization
monitoring observations, as well as ultra-high resolution (~0.15
milliarcsecond) imaging of the jet structure at lambda=7mm. The time
coincidence in the end of 2008 of the propagation of the brightest superluminal
feature detected in AO 0235+164 (Qs) with an extreme multi-spectral-range
(gamma-ray to radio) outburst, and an extremely high optical and 7mm (for Qs)
polarization degree provides strong evidence supporting that all these events
are related. This is confirmed at high significance by probability arguments
and Monte-Carlo simulations. These simulations show the unambiguous correlation
of the gamma-ray flaring state in the end of 2008 with those in the optical,
millimeter, and radio regime, as well as the connection of a prominent X-ray
flare in October 2008, and of a series of optical linear polarization peaks,
with the set of events in the end of 2008. The observations are interpreted as
the propagation of an extended moving perturbation through a re-collimation
structure at the end of the jet's acceleration and collimation zone.

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    ABSTRACT: We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component, instead of being ejected from the core. Their oblique nature should also result in distinct polarization properties. Those appearing closer to the core show small apparent motions and a very slow secular decrease in brightness, and could be identified as stationary components. Those appearing farther downstream are weaker and can reach superluminal apparent motions. The existence of these trailing components indicates that not all observed components necessarily represent major perturbations at the jet inlet; rather, multiple emission components can be generated by a single disturbance in the jet. While the superluminal component associated with the primary perturbation exhibits a rather stable pattern speed, trailing components have velocities that increase with distance from the core but move at less than the jet speed. The trailing components exhibit motion and structure consistent with the triggering of pinch modes by the superluminal component. Comment: Accepted by ApJ Letters. LaTeX, 19 pages, 4 PostScript figures
    The Astrophysical Journal 01/2001; · 6.73 Impact Factor
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    ABSTRACT: We combine time-dependent multi-waveband flux and linear polarization observations with submilliarcsecond-scale polarimetric images at λ = 7 mm of the BL Lacertae type blazar OJ287 to locate the γ-ray emission in prominent flares in the jet of the source >14 pc from the central engine. We demonstrate a highly significant correlation between the strongest γ-ray and millimeter-wave flares through Monte Carlo simulations. The two reported γ-ray peaks occurred near the beginning of two major millimeter-wave outbursts, each of which is associated with a linear polarization maximum at millimeter wavelengths. Our very long baseline array observations indicate that the two millimeter-wave flares originated in the second of two features in the jet that are separated by >14 pc. The simultaneity of the peak of the higher-amplitude γ-ray flare and the maximum in polarization of the second jet feature implies that the γ-ray and millimeter-wave flares are cospatial and occur >14 pc from the central engine. We also associate two optical flares, accompanied by sharp polarization peaks, with the two γ-ray events. The multi-waveband behavior is most easily explained if the γ-rays arise from synchrotron self-Compton scattering of optical photons from the flares. We propose that flares are triggered by interaction of moving plasma blobs with a standing shock. The γ-ray and optical emission is quenched by inverse Compton losses as synchrotron photons from the newly shocked plasma cross the emission region. The millimeter-wave polarization is high at the onset of a flare, but decreases as the electrons emitting at these wavelengths penetrate less polarized regions.
    The Astrophysical Journal Letters 12/2010; 726(1):L13. · 6.35 Impact Factor
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    ABSTRACT: We present numerical simulations of the generation, evolution, and radio emission of superluminal components in relativistic jets. We perform the fluid dynamical calculations using a relativistic time-dependent code based on a high-resolution shock-capturing scheme, and then we calculate the radio emission by integrating the transfer equations for synchrotron radiation. These simulations show that a temporary increase in the flow velocity at the base of the jet produces a moving perturbation that contains both a forward and a reverse shock and is trailed by a rarefaction. The perturbation appears in the simulated maps as a region of enhanced emission moving downstream at a superluminal apparent velocity. Interactions of the perturbation with the underlying steady jet result in changes in the internal brightness distribution of the superluminal component, which are manifested as low-level fluctuations about the long-term evolution of both the apparent velocity and the exponential decay of the light curves.
    The Astrophysical Journal 06/1997; · 6.73 Impact Factor

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