CONSTRAINING EMISSION MODELS OF LUMINOUS BLAZAR SOURCES

By M. Sikora, Ł. Stawarz, R. Moderski, K. Nalewajko, G. Madejski. 2009

257 citations recorded by the source corpus.

Many luminous blazars which are associated with quasar-type active galactic nuclei display broadband spectra characterized by a large luminosity ratio of their high-energy (γ-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars also typically have very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high-energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad-line region, or dusty molecular torus. The lack or weakness of bulk-Compton and Klein–Nishina features indicated by the presently available data favors the production of γ-rays via upscattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical, and γ-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intraday flares occasionally observed in powerful blazar sources.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/1f7246478f4ab0c4658bede1f6445a38fab1709d

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Citations in the corpus

BLAZARS AS ULTRA-HIGH-ENERGY COSMIC-RAY SOURCES: IMPLICATIONS FOR TeV GAMMA-RAY OBSERVATIONS (2011, unknown): “…are derived by using the common relations εs/mec2 ≈ δ(B′/BQ)γ′b 2 /(1 + z), and εc/mec2 ≈ (4/3)γ′b 2 εs (i.e., the typical fluid-frame Lorentz factor of electrons radiating near the peak synchrotron and SSC frequencies isγ′b ≈ ( √ 3/2) √ εc/εs in the Thomson limit) (e.g., Sikora et al. 2009).”
Relativistic Jets Shine through Shocks or Magnetic Reconnection (2015, background): “In blazars both the synchrotron and the Compton humps are visible and their relative brightness constrains the ratioof energy densitiesUB/Ue at the emitting region (e.g., Sikora et al. 2009).”
ACCELERATION OF PARTICLES AT THE TERMINATION SHOCK OF A RELATIVISTIC STRIPED WIND (2011, background): “In the case of luminous blazar sources, very flat electron spectra below GeV energies are inferred directly from X-ray observations (Celotti & Ghisellini 2008; Sikora et al. 2009).”
RELATIVISTIC RECONNECTION: AN EFFICIENT SOURCE OF NON-THERMAL PARTICLES (2014, background): “Flat electron spectra below GeV energies are required to fit the broad-band emission of hotspots in radio galaxies (Stawarz et al. 2007) and the X-ray spectrum of blazars (Celotti & Ghisellini 2008; Sikora et al. 2009).”
INSIGHTS INTO THE HIGH-ENERGY γ-RAY EMISSION OF MARKARIAN 501 FROM EXTENSIVE MULTIFREQUENCY OBSERVATIONS IN THE FERMI ERA (2011, background): “At even lower electron energies, other energization processes must play a dominant role (e.g., Hoshino et al. 1992), resulting in formation of very flat electron spectra (see the related discussion in Sikora et al. 2009).”
MINUTE-TIMESCALE >100 MeV γ-RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI-LAT IN 2015 JUNE (2016, methodology): “In the standard leptonic model of FSRQs, γ rays are produced by the External Radiation Comptonization (ERC) mechanism (e.g.,Sikora et al. 2009).”
THE NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY (NuSTAR) HIGH-ENERGY X-RAY MISSION (2013, background): “The relative temporal variability in different spectral bands, from radio through TeV, provides an important handle on the location of the energy dissipation as a function of distance from the central black hole (Sikora et al. 2009).”
A hadronic origin for ultra-high-frequency-peaked BL Lac objects (2014, background): “The cooling terms are represented by the adiabatic losses (τad = 2 R/c), the synchrotron losses (the inverse of the synchrotron cooling rate, see Equation 15) and the photomeson losses (expressed analytically following Sikora et al. 2009).”