LOCATING THE BLAZAR EMISSION SITE WITH FERMI VARIABILITY

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.

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Spectral Variability in Seyfert Galaxies

Symposium - International Astronomical Union ◽

10.1017/s007418090015507x ◽

1987 ◽

Vol 121 ◽

pp. 161-167

Author(s):

B.M. Peterson

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Broad Line ◽

Spectral Variability ◽

Broad Line Region ◽

Broad Emission ◽

Line Region ◽

Order Of Magnitude ◽

Optical Continuum

Recent observations of spectral variability in active galactic nuclei have established the connection between the broad emission-line and optical continuum flux changes. The inferred size of the broad-line region is at least an order of magnitude smaller than conventional estimates based on photoionization models, which leads to new conclusions about the nature of the broad-line region.

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Broad-line region structure and line profile variations in the changing look AGN HE 1136-2304

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833727 ◽

2018 ◽

Vol 619 ◽

pp. A168 ◽

Cited By ~ 6

Author(s):

W. Kollatschny ◽

M. W. Ochmann ◽

M. Zetzl ◽

M. Haas ◽

D. Chelouche ◽

...

Keyword(s):

Seyfert Galaxies ◽

Spectroscopic Properties ◽

Emission Lines ◽

Broad Line ◽

Spectral Variability ◽

Continuum Source ◽

Line Intensities ◽

Broad Line Region ◽

Line Region ◽

Optical Continuum

Aims. A strong X-ray outburst was detected in HE 1136-2304 in 2014. Accompanying optical spectra revealed that the spectral type has changed from a nearly Seyfert 2 type (1.95), classified by spectra taken 10 and 20 years ago, to a Seyfert 1.5 in our most recent observations. We seek to investigate a detailed spectroscopic campaign on the spectroscopic properties and spectral variability behavior of this changing look AGN and compare this to other variable Seyfert galaxies. Methods. We carried out a detailed spectroscopic variability campaign of HE 1136-2304 with the 10 m Southern African Large Telescope (SALT) between 2014 December and 2015 July. Results. The broad-line region (BLR) of HE 1136-2304 is stratified with respect to the distance of the line-emitting regions. The integrated emission line intensities of Hα, Hβ, He I λ5876, and He II λ4686 originate at distances of 15.0−3.8+4.2, 7.5−5.7+4.6, 7.3−4.4+2.8, and 3.0−3.7+5.3 light days with respect to the optical continuum at 4570 Å. The variability amplitudes of the integrated emission lines are a function of distance to the ionizing continuum source as well. We derived a central black hole mass of 3.8 ± 3.1 × 107 M⊙ based on the linewidths and distances of the BLR. The outer line wings of all BLR lines respond much faster to continuum variations indicating a Keplerian disk component for the BLR. The response in the outer wings is about two light days shorter than the response of the adjacent continuum flux with respect to the ionizing continuum flux. The vertical BLR structure in HE 1136-2304 confirms a general trend that the emission lines of narrow line active galactic nuclei (AGNs) originate at larger distances from the midplane in comparison to AGNs showing broader emission lines. Otherwise, the variability behavior of this changing look AGN is similar to that of other AGN.

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Gamma rays from jets interacting with BLR clouds in blazars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834231 ◽

2019 ◽

Vol 623 ◽

pp. A101 ◽

Cited By ~ 3

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.

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Magnetization of AGN jets as imposed by leptonic models of luminous blazars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315001945 ◽

2014 ◽

Vol 10 (S313) ◽

pp. 85-86

Author(s):

Mateusz Janiak ◽

Marek Sikora ◽

Rafal Moderski

Keyword(s):

Black Hole ◽

Kinetic Energy ◽

Energy Flux ◽

Broad Line ◽

Jet Formation ◽

Frequency Dependent ◽

Broad Line Region ◽

Line Region ◽

Γ Ray ◽

Dusty Torus

AbstractRecent measurements of frequency-dependent shift of radio-core locations indicate that the ratio of the magnetic to kinetic energy flux (the σ parameter) is of the order of unity. These results are consistent with predictions of magnetically-arrested-disk (MAD) models of a jet formation, but contradict the predictions of leptonic models of γ-ray production in luminous blazars. We demonstrate this discrepancy by computing the γ-ray-to-synchrotron luminosity ratio (the q parameter) as a function of a distance from the black hole for different values of σ and using both spherical and planar models for broad-line region and dusty torus. We find that it is impossible to reproduce observed q ≫ 1 for jets with σ ≥ 1. This may indicate that blazar radiation is produced in reconnection layers or in spines of magnetically stratified jets.

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Steps toward Determination of the Size and Structure of the Broad‐Line Region in Active Galactic Nuclei. XVI. A 13 Year Study of Spectral Variability in NGC 5548

The Astrophysical Journal ◽

10.1086/344197 ◽

2002 ◽

Vol 581 (1) ◽

pp. 197-204 ◽

Cited By ~ 137

Author(s):

B. M. Peterson ◽

P. Berlind ◽

R. Bertram ◽

K. Bischoff ◽

N. G. Bochkarev ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Broad Line ◽

Spectral Variability ◽

Broad Line Region ◽

Line Region ◽

Ngc 5548 ◽

Size And Structure

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Hadronuclear interpretation of the possible neutrino emission from PKS B1424-418, GB6 J1040+0617 and PKS 1502+106

Research in Astronomy and Astrophysics ◽

10.1088/1674-4527/21/12/305 ◽

2022 ◽

Vol 21 (12) ◽

pp. 305

Author(s):

Ze-Rui Wang ◽

Rui Xue

Keyword(s):

Detection Rate ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Broad Line ◽

Central Black Hole ◽

Proton Proton ◽

Broad Line Region ◽

Neutrino Detection ◽

Line Region ◽

Jet Power

Abstract In addition to neutrino event IceCube-170922A which is observed to be associated with a γ-ray flare from blazar TXS 0506+056, there are also several neutrino events that may be associated with blazars. Among them, PKS B1424-418, GB6 J1040+0617 and PKS 1502+106 are low synchrotron peaked sources, which are usually believed to have the broad line region in the vicinity of the central black hole. They are considered as counterparts of IceCube event 35, IceCube-141209A and IceCube-190730A, respectively. By considering the proton-proton (pp) interactions between the dense gas clouds in the broad line region and the relativistic protons in the jet, we show that the pp model that is applied in this work can not only reproduce the multi-waveband spectral energy distribution but also suggest a considerable annual neutrino detection rate. We also discuss the emission from the photopion production and Bethe-Heitler pair production with a sub-Eddington jet power that is suggested in our model and find that it has little effect on the spectrum of total emission for all of three sources.

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