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.

LOCATING THE BLAZAR EMISSION SITE WITH FERMI VARIABILITY

2012 ◽  
Vol 08 ◽  
pp. 37-42
Author(s):  
MARKOS GEORGANOPOULOS ◽  
AMANDA DOTSON ◽  
DEMOSTHENES KAZANAS ◽  
ERIC PERLMAN
Keyword(s):  
Energy Dissipation ◽  
Broad Line ◽  
Jet Formation ◽  
Spectral Variability ◽  
Ongoing Debate ◽  
Broad Line Region ◽  
Photon Field ◽  
First Case ◽  
Line Region

This work presents a method for settling the following ongoing debate: is the GeV emission of powerful blazars produced inside the sub-pc size broad line region (BLR) or further out at scales of ~ 10 pc where the IR photon field of the dusty molecular torus dominates over that the UV field of the BLR? In the first case the GeV emission is most probably external Compton (EC) scattering of the ~ 10 eV BLR photons21, while in the second the seed photons for the EC GeV emission are the ~ 0.1 eV photons of the dust9 in the molecular torus8. The issue of the energy dissipation location is connected to the jet formation and collimation process25 and, as we argue here, can be resolved with Fermi spectral variability observations.

scholarly journals Radiation from the impact of broad-line region clouds onto AGN accretion disks

2020 ◽  
Vol 636 ◽  
pp. A92
Author(s):  
A. L. Müller ◽  
G. E. Romero
Keyword(s):  
Accretion Disk ◽  
Spectral Energy Distribution ◽  
Strong Shock ◽  
Shock Acceleration ◽  
Spectral Energy ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
The Impact ◽  
Relativistic Particles

Context. Active galactic nuclei are supermassive black holes surrounded by an accretion disk, two populations of clouds, bipolar jets, and a dusty torus. The clouds move in Keplerian orbits at high velocities. In particular, the broad-line region (BLR) clouds have velocities ranging from 1000 to 10 000 km s−1. Given the extreme proximity of these clouds to the supermassive black hole, frequent collisions with the accretion disk should occur. Aims. The impact of BLR clouds onto the accretion disk can produce strong shock waves where particles might be accelerated. The goal of this work is to investigate the production of relativistic particles, and the associated non-thermal radiation in these events. In particular, we apply the model we develop to the Seyfert galaxy NGC 1068. Methods. We analyze the efficiency of diffusive shock acceleration in the shock of colliding clouds of the BLR with the accretion disk. We calculate the spectral energy distribution of photons generated by the relativistic particles and estimate the number of simultaneous impacts needed to explain the gamma radiation observed by Fermi in Seyfert galaxies. Results. We find that is possible to understand the measured gamma emission in terms of the interaction of clouds with the disk if the hard X-ray emission of the source is at least obscured between 20% and 40%. The total number of clouds contained in the BLR region might be between 3 × 108 and 6 × 108, which are values in good agreement with the observational evidence. The maximum energy achieved by the protons (∼PeV) in this context allows the production of neutrinos in the observing range of IceCube.

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 Broad line region and black hole mass of PKS 1510-089 from spectroscopic reverberation mapping

2020 ◽  
Vol 642 ◽  
pp. A59
Author(s):  
Suvendu Rakshit
Keyword(s):  
Black Hole ◽  
Root Mean Square ◽  
Thermal Emission ◽  
Light Curves ◽  
Broad Line ◽  
Mean Square ◽  
Black Hole Mass ◽  
Broad Line Region ◽  
Line Region ◽  
The Continuum

Reverberation results of the flat spectrum radio quasar PKS 1510-089 from 8.5 years of spectroscopic monitoring carried out at Steward Observatory over nine observing seasons between December 2008 and June 2017 are presented. Optical spectra show strong Hβ, Hγ, and Fe II emission lines overlying on a blue continuum. All the continuum and emission line light curves show significant variability with fractional root-mean-square variations of 37.30 ± 0.06% (f5100), 11.88 ± 0.29% (Hβ), and 9.61 ± 0.71% (Hγ); however, along with thermal radiation from the accretion disk, non-thermal emission from the jet also contributes to f5100. Several methods of time series analysis (ICCF, DCF, von Neumann, Bartels, JAVELIN, χ2) are used to measure the lag between the continuum and line light curves. The observed frame broad line region size is found to be 61.1−3.2+4.0 (64.7−10.6+27.1) light-days for Hβ (Hγ). Using the σline of 1262 ± 247 km s−1 measured from the root-mean-square spectrum, the black hole mass of PKS 1510-089 is estimated to be 5.71−0.58+0.62 × 107 M⊙.

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 Prospects for γ-ray observations of narrow-line Seyfert 1 galaxies with the Cherenkov Telescope Array – II. γ–γ absorption in the broad-line region radiation fields

2020 ◽  
Vol 494 (1) ◽  
pp. 411-424 ◽  
Author(s):  
P Romano ◽  
M Böttcher ◽  
L Foschini ◽  
C Boisson ◽  
S Vercellone ◽  
...  
Keyword(s):  
High Energy ◽  
Emission Region ◽  
Broad Line ◽  
Narrow Line ◽  
Telescope Array ◽  
Cherenkov Telescope ◽  
Broad Line Region ◽  
Radiation Fields ◽  
Line Region ◽  
Γ Ray

ABSTRACT Gamma-ray emitting narrow-line Seyfert 1 (γ-NLS1) galaxies possibly harbour relatively low-mass black holes (106–108 M⊙) accreting close to the Eddington limit, and share many characteristics with their sibling sources, flat-spectrum radio quasars. Although they have been detected in the MeV–GeV band with Fermi–LAT, they have never been seen in the very high energy band with current imaging atmospheric Cherenkov telescopes (IACTs). Thus, they are key targets for the next-generation IACT, the Cherenkov Telescope Array (CTA). In a previous work we selected, by means of extensive simulations, the best candidates for a prospective CTA detection (SBS 0846+513, PMN J0948+0022, and PKS 1502+036) taking into account the effects of both the intrinsic absorption (approximated with a cut-off at 30 GeV), and the extragalactic background light on the propagation of γ-rays. In this work, we simulate the spectra of these three sources by adopting more realistic broad-line region (BLR) absorption models. In particular, we consider the detailed treatment of γ–γ absorption in the radiation fields of the BLR as a function of the location of the γ-ray emission region with parameters inferred from observational constraints. We find that, due to the energy range extent and its sensitivity, CTA is particularly well suited to locate the γ-ray emitting region in γ-NLS1. In particular CTA will be able not only to distinguish whether the γ-ray emitting region is located inside or outside the BLR, but also where inside the BLR it may be.

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.

scholarly journals Constraints on the emission region of 3C 279 during strong flares in 2014 and 2015 through VHE γ-ray observations with H.E.S.S.

2019 ◽  
Vol 627 ◽  
pp. A159 ◽  
Author(s):  
◽  
H. Abdalla ◽  
R. Adam ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Black Hole ◽  
Lorentz Invariance ◽  
High Energy ◽  
Emission Region ◽  
Physical Parameters ◽  
Broad Line ◽  
Data Set ◽  
Broad Line Region ◽  
Link Type ◽  
Line Region

The flat spectrum radio quasar 3C 279 is known to exhibit pronounced variability in the high-energy (100 MeV <  E <  100 GeV) γ-ray band, which is continuously monitored with Fermi-LAT. During two periods of high activity in April 2014 and June 2015 target-of-opportunity observations were undertaken with the High Energy Stereoscopic System (H.E.S.S.) in the very-high-energy (VHE, E >  100 GeV) γ-ray domain. While the observation in 2014 provides an upper limit, the observation in 2015 results in a signal with 8.7σ significance above an energy threshold of 66 GeV. No VHE variability was detected during the 2015 observations. The VHE photon spectrum is soft and described by a power-law index of 4.2 ± 0.3. The H.E.S.S. data along with a detailed and contemporaneous multiwavelength data set provide constraints on the physical parameters of the emission region. The minimum distance of the emission region from the central black hole was estimated using two plausible geometries of the broad-line region and three potential intrinsic spectra. The emission region is confidently placed at r ≳ 1.7 × 1017 cm from the black hole, that is beyond the assumed distance of the broad-line region. Time-dependent leptonic and lepto-hadronic one-zone models were used to describe the evolution of the 2015 flare. Neither model can fully reproduce the observations, despite testing various parameter sets. Furthermore, the H.E.S.S. data were used to derive constraints on Lorentz invariance violation given the large redshift of 3C 279.

scholarly journals Relativistic jets at high energies

2010 ◽  
Vol 6 (S275) ◽  
pp. 24-31
Author(s):  
Amir Levinson
Keyword(s):  
Recent Progress ◽  
Thermal Emission ◽  
Broad Line ◽  
Relativistic Jets ◽  
Broad Line Region ◽  
High Energies ◽  
Line Region ◽  
Bulk Energy ◽  
Γ Ray

AbstractA recent progress in the study of γ-ray jets is reviewed, with a focus on some theoretical interpretations of the VHE emission from M87, and possibly other misaligned blazars; the connection between the GeV breaks exhibited by bright LAT blazars and opacity sources in the broad line region; the consequences of the detection of GeV emission from GRBs to models of magnetic outflows; and the implications of the thermal emission observed is some GRBs to dissipation of the outflow bulk energy.

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