scholarly journals Millimetre Continuum Variations, VLBI Structure and Gamma-rays: Investigating Shocked Jet Physics

2002 ◽  
Vol 19 (1) ◽  
pp. 117-121 ◽  
Author(s):  
E. Valtaoja ◽  
T. Savolainen ◽  
K. Wiik ◽  
A. Lähteenmäki
Keyword(s):  
Flux Density ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Large Fraction ◽  
Jet Physics ◽  
Broad Line ◽  
Structural Variations ◽  
Broad Line Region ◽  
Line Region ◽  
Inverse Compton

AbstractWe compare the total flux density variations and the VLBI structural variations in a sample of 27 gamma-ray blazars. We find that all the radio variations are due to shocks; the flux of the underlying jet remains constant. A large fraction of the shocks grow and fade within the innermost 0.1 mas, appearing only as ‘core flares’. Comparisons with the EGRET data show that gamma-ray flares must come from the shocks, not from the jet. At the time of an EGRET flare, the shock is typically already over a parsec downstream from the radio core, beyond the accretion disk and/or the broad line region (BLR) photon fields. Thus, present models for gamma-ray production are inadequate, since they typically model the gamma-ray inverse Compton flux as coming from the jet, with significant disk or BLR external Compton components.

scholarly journals Excluding possible sites of high-energy emission in 3C 84

2020 ◽  
Vol 500 (4) ◽  
pp. 4671-4677
Author(s):  
Lena Linhoff ◽  
Alexander Sandrock ◽  
Matthias Kadler ◽  
Dominik Elsässer ◽  
Wolfgang Rhode
Keyword(s):  
Black Hole ◽  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Emission Region ◽  
Broad Line ◽  
Central Black Hole ◽  
Broad Line Region ◽  
Ring Geometry ◽  
Line Region

ABSTRACT The FR-I galaxy 3C 84, that is identified with the misaligned blazar NGC 1275, is well known as one of the very few radio galaxies emitting gamma-rays in the TeV range. Yet, the gamma-ray emission region cannot be pinpointed and the responsible mechanisms are still unclear. We calculate the optical absorption depth of high-energy photons in the broad-line region of 3C 84 depending on their energy and distance to the central black hole. Based on these calculations, a lower limit on the distance of the emission region from the central black hole can be derived. These lower limits are estimated for two broad-line region geometries (shell and ring) and two states of the source, the low state in 2016 October–December and a flare state in 2017 January. For the shell geometry, we can place the emission region outside the Ly α radius. For the ring geometry and the low flux activity, the minimal distance between the black hole, and the gamma-ray emission region is close to the Ly α radius. In the case of the flaring state (ring geometry), the results are not conclusive. Our results exclude the region near the central black hole as the origin of the gamma-rays detected by Fermi–LAT and Major Atmospheric Gamma-Ray Imaging Cherenkov. With these findings, we can constrain the theoretical models of acceleration mechanisms and compare the possible emission region to the source’s morphology resolved by radio images from the Very Long Baseline Array.

scholarly journals On the origin of gamma-rays in Fermi blazars: beyondthe broad-line region

2018 ◽  
Vol 477 (4) ◽  
pp. 4749-4767 ◽  
Author(s):  
L Costamante ◽  
S Cutini ◽  
G Tosti ◽  
E Antolini ◽  
A Tramacere
Keyword(s):  
Gamma Rays ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region

scholarly journals Gamma rays from jets interacting with BLR clouds in blazars

2019 ◽  
Vol 623 ◽  
pp. A101 ◽  
Author(s):  
S. del Palacio ◽  
V. Bosch-Ramon ◽  
G. E. Romero
Keyword(s):  
Thermal Emission ◽  
Strong Shock ◽  
High Energy ◽  
Broad Line ◽  
High Energy Radiation ◽  
Broad Line Region ◽  
Photon Field ◽  
Cloud Dynamics ◽  
Line Region ◽  
Inverse Compton

Context. The innermost parts of powerful jets in active galactic nuclei are surrounded by dense, high-velocity clouds from the broad-line region, which may penetrate into the jet and lead to the formation of a strong shock. Such jet-cloud interactions are expected to have measurable effects on the γ-ray emission from blazars. Aims. We characterise the dynamics of a typical cloud-jet interaction scenario, and the evolution of its radiative output in the 0.1–30 GeV energy range, to assess to what extent these interactions can contribute to the γ-ray emission in blazars. Methods. We use semi-analytical descriptions of the jet-cloud dynamics, taking into account the expansion of the cloud inside the jet and its acceleration. Assuming that electrons are accelerated in the interaction and making use of the hydrodynamical information, we then compute the high-energy radiation from the cloud, including the absorption of γ-rays in the ambient photon field through pair creation. Results. Jet-cloud interactions can lead to significant γ-ray fluxes in blazars with a broad-line region (BLR), in particular when the cloud expansion and acceleration inside the jet are taken into account. This is caused by 1) the increased shocked area in the jet, which leads to an increase in the energy budget for the non-thermal emission; 2) a more efficient inverse Compton cooling with the boosted photon field of the BLR; and 3) an increased observer luminosity due to Doppler boosting effects. Conclusions. For typical broad-line region parameters, either (i) jet-cloud interactions contribute significantly to the persistent γ-ray emission from blazars or (ii) the BLR is far from spherical or the fraction of energy deposited in non-thermal electrons is small.

scholarly journals Pair Cascades at the Edge of the Broad-line Region Shaping the Gamma-Ray Spectrum of 3C 279

2021 ◽  
Vol 917 (1) ◽  
pp. 32
Author(s):  
Christoph Wendel ◽  
Amit Shukla ◽  
Karl Mannheim
Keyword(s):  
Gamma Ray ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region

scholarly journals The Effect of Radiation Drag on Relativistic Bulk Flows in Active Galactic Nuclei

2002 ◽  
Vol 19 (1) ◽  
pp. 122-124
Author(s):  
Qinghuan Luo
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Broad Line ◽  
Nuclear Region ◽  
Inverse Compton Scattering ◽  
Broad Line Region ◽  
Line Region ◽  
Inverse Compton ◽  
Γ Ray ◽  
Dusty Torus

AbstractThe effect of radiation drag on relativistic bulk flows is re-examined. Highly relativistic bulk flows in the nuclear region are subject to Compton drag, i.e. radiation deceleration as a result of inverse Compton scattering of ambient soft photon fields from emission from the accretion disk, broad line region, or dusty torus. Possible observational consequences of X-/γ-ray emission produced from Compton drag are specifically discussed.

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