The Evolution of Shocks in Blazar Jets

Bicknell, G. V.; Wagner, S. J.

doi:10.1071/as02009

Cited by 15 publications

(16 citation statements)

References 11 publications

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“…The nonthermal emission from BL Lac is usually modeled by the synchrotron self-Compton scenario (SSC, see e.g., Maraschi et al 1992;Bicknell & Wagner 2002), where relativistic electrons cool either via the synchrotron or the inverse Compton mechanism. The comptonized photons are assumed to be predominantly the synchrotron photons themselves, rather than photons coming from the outside the emission region as in the external Compton model (EC, see e.g.…”

Section: Discussionmentioning

confidence: 99%

Lognormal variability in BL Lacertae

Giebels

Degrange

2009

A&A

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Context. The characterization of a time series is a powerful tool for investigating the nature of mechanisms that generate variability in astrophysical objects. Blazar variability across the entire electromagnetic spectrum is a long-standing puzzle, and it has been difficult to ascertain the mechanisms at play. Aims. Lognormal variability in X-ray light curves, probably related to accretion disk activity, has been discovered in various compact systems, such as Seyfert galaxies and X-ray binaries. Identifying a similar behaviour in blazars would establish a link between them. Methods. Public X-ray data from the blazar BL Lac are used to investigate the nature of its variability, and more precisely the flux dependency of the variability and the distribution of fluxes.Results. The variations in the flux are found to have a lognormal distribution and the average amplitude of variability is proportional to the flux level. Conclusions. BL Lac is the first blazar in which lognormal X-ray variability is clearly detected. The light curve is orders of magnitude less variable than other blazars, with few bursting episodes. If this defines a specific state of the source, then the lognormality might be the imprint of the accretion disk on the jet, linking for the first time accretion and jet properties in a blazar.

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Section: Discussionmentioning

confidence: 99%

Lognormal variability in BL Lacertae

Giebels

Degrange

2009

A&A

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“…Structure and dynamics of such internal shocks is in general very complex and depends on a number of parameters, such as the relative velocity of inhomogeneities, their densities, temperatures, geometry, and total masses. The shock structure can be double, single (forward or reverse), or can initially it can be double, followed by an evolution into a single shock (Daigne & Mochkovitch 1998;Bicknell & Wagner 2002). Regardless, in the case of inhomogeneities which are cold prior to their collision and which have comparable masses and comparable rest frame densities, the constant speed of the shocked plasma is a good approximation.…”

Section: The Modelmentioning

confidence: 99%

Numerical simulations of radiation from blazar jets

Moderski

Sikora

Błażejowski

2003

A&A

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Abstract. We present a description of our numerical code BLAZAR. This code calculates spectra and light curves of blazars during outbursts. The code is based on a model in which the non-thermal flares in blazars are produced in thin shells propagating down a conical jet with relativistic velocities. Such shells may represent layers of a shocked plasma, enclosed between the forward and reverse fronts of an internal shock. In the model adopted by us, the production of non-thermal radiation is assumed to be dominated by electrons and positrons which are accelerated directly, rather then injected by pair cascades. The code includes synchrotron emission and inverse-Compton process as the radiation mechanisms. Both synchrotron photons and external photons are included as the seed photons for Comptonization. At the present stage, the code is limited to treat the inverse Compton process only within the Thomson limit and is specialized to model radiation production in the flat spectrum radio quasars. As an example, we present the results of modeling an outburst in 3C 279 -the most extensively monitored γ-ray -bright quasar.

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“…Recent high-resolution observations of AGN jets show fine structure of knots in the beam flow for up to several tens of kiloparsecs in M87 (Biretta et al 1999;Marshall et al 2002;Wilson & Yang 2002), 3C 273 (Bahcall et al 1995;Marshall et al 2001;Sambruna et al 2002;Jester et al 2002), Centaurus A (Kraft et al 2002), 3C 303 (Kataoka et al 2003), and others (Sambruna et al 2001). Knots on subparsec or parsec scales are thought to be from intermittent flows from the central source, and knots in ''blazars'' are due to exceptionally strong shocks that are caused by the collisions of internal shocks (Spada et al 2001;Bicknell & Wagner 2002). Knots on kiloparsec or larger scales are not well understood.…”

Section: Introductionmentioning

confidence: 99%

Propagation and Dynamics of Relativistic Jets

Mizuta

Yamada

Takabe

2004

ApJ

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We investigate the dynamics and morphology of jets propagating into the interstellar medium using twodimensional relativistic hydrodynamic simulations. The calculations are performed assuming axisymmetric geometry and follow jet propagation over a long distance. The jets are assumed to be ''light,'' with the density ratio between the beam to the ambient gas much less than unity. We examine the mechanism for the appearance of vortices at the head of jets in the hot spot. Such vortices are known as a trigger of a deceleration phase, which appears after a short phase in which the jet propagation follows the results from one-dimensional analysis. We find that an oblique shock at the boundary rim near the end of the beam strongly affects the flow structure in and around the hot spot. Weakly shocked gas passes through this oblique shock and becomes a trigger for the generation of vortices. We also find the parameter dependence of these effects for the propagation and dynamics of the jets. The jet with slower propagation velocity is weakly pinched, has large vortices, and shows very complex structure at the head of the jets and extended synchrotron emissivity.

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The Evolution of Shocks in Blazar Jets

Cited by 15 publications

References 11 publications

Lognormal variability in BL Lacertae

Lognormal variability in BL Lacertae

Numerical simulations of radiation from blazar jets

Propagation and Dynamics of Relativistic Jets

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