Spectral evolution of active galactic nuclei - A unified description of the X-ray and gamma-ray backgrounds

1982 ◽  
Vol 260 ◽  
pp. 1 ◽  
Author(s):  
D. Leiter ◽  
E. Boldt
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Spectral Evolution ◽  
X Ray ◽  
Unified Description

scholarly journals Gamma-Ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 36
Author(s):  
Yoshiyuki Inoue ◽  
Dmitry Khangulyan ◽  
Akihiro Doi
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Thermal Activity ◽  
X Ray ◽  
Cascade Models ◽  
Coronal Activity ◽  
Ngc 1068 ◽  
High Energy Particles

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 yr survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.

scholarly journals Hot Accretion Disks and the High Energy Background

1983 ◽  
Vol 104 ◽  
pp. 345-346
Author(s):  
M. Kafatos ◽  
Jean A. Eilek
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Spectral Range ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
High Energy ◽  
X Rays ◽  
X Ray

The origin of the high energy (X-ray and gamma-ray) background may be attributed to discrete sources, which are usually thought to be active galactic nuclei (AGN) (cf. Rothschild et al. 1982, Bignami et al. 1979). At X-rays a lot of information has been obtained with HEAO-1 in the spectral range 2–165 keV. At gamma-rays the background has been estimated from the Apollo 15 and 16 (Trombka et al. 1977) and SAS-2 (Bignami et al. 1979) observations. A summary of some of the observations (Rothschild et al. 1982) is shown in Figure 1. The contribution of AGN to the diffuse high energy background is uncertain at X-rays although it is generally estimated to be in the 20–30% range (Rothschild et al. 1982). At gamma-rays, in the range 1–150 MeV, AGN (specifically Seyfert galaxies) could account for all the emission.

scholarly journals Long-term photometry of blazars at Abastumani Observatory

2006 ◽  
Vol 2 (S238) ◽  
pp. 397-398
Author(s):  
Omar M. Kurtanidze ◽  
Maria G. Nikolashvili ◽  
Givi N. Kimeridze ◽  
Lorand A. Sigua ◽  
Bidzina Z. Kapanadze ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Monitoring Program ◽  
Galactic Nuclei ◽  
X Ray

AbstractWe give a brief summary of the ongoing Abastumani Active Galactic Nuclei Monitoring Program started in the May 1997. More than 110000 frames are obtained during more than 1300 nights of observations for about 50 target objects, among them gamma-ray, X-ray and optical blazars. All observations were done in the BVRI bands using ST-6 CCD based photometer attached to the Newtonian focus of 70-cm meniscus telescope.

scholarly journals Gamma-Rays from Active Galactic Nuclei

1983 ◽  
Vol 6 ◽  
pp. 505-510
Author(s):  
M. Kafatos
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Thermal Processes ◽  
Relativistic Electrons ◽  
Massive Black Holes ◽  
X Ray ◽  
Electrons And Positrons ◽  
Γ Rays

Gamma-ray observations from active galactic nuclei (AGN) are important in trying to understand the nature of their central sources. A handful of mechanisms can give rise to γ-rays either from nonthermal or from thermal processes. Hot accretion disks around massive black holes in the centers of AGN could provide the required thermal electrons, pions and relativistic electrons and positrons to explain both the X-ray and γ-ray emission.

M 87 — TEN YEARS OF TEV GAMMA-RAY OBSERVATIONS

2010 ◽  
Vol 19 (06) ◽  
pp. 849-857
Author(s):  
MATTHIAS BEILICKE
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Radio Galaxy ◽  
Galactic Nuclei ◽  
Plasma Jet ◽  
Radio Galaxies ◽  
Jet Physics ◽  
X Ray ◽  
High Energies ◽  
Very High

The giant radio galaxy M 87 is located 16.7 Mpc away and harbours a supermassive black hole in its center. Structures of its relativistic plasma jet are resolved at radio, optical and X–ray energies. M 87 belongs to the class of active galactic nuclei and is one of only a few radio galaxies detected at very-high energies (E > 100 GeV ). This makes it a unique laboratory to study jet physics and the corresponding emission processes. The results obtained from TeV gamma-ray observations during the last decade are discussed.

scholarly journals New hard X-ray sources discovered in the ongoing INTEGRAL Galactic plane survey after 14 yr of observations

2017 ◽  
Vol 470 (1) ◽  
pp. 512-516 ◽  
Author(s):  
Roman A. Krivonos ◽  
Sergey S. Tsygankov ◽  
Ilya A. Mereminskiy ◽  
Alexander A. Lutovinov ◽  
Sergey Yu. Sazonov ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Plane ◽  
Cataclysmic Variables ◽  
Galactic Nuclei ◽  
Pulsar Wind Nebulae ◽  
X Ray ◽  
Sky Survey ◽  
The Galaxy ◽  
Pulsar Wind

Abstract The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) continues to successfully work in orbit after its launch in 2002. The mission provides the deepest ever survey of hard X-ray sources throughout the Galaxy at energies above 20 keV. We report on a catalogue of new hard X-ray source candidates based on the latest sky maps comprising 14 yr of data acquired with the IBIS telescope onboard INTEGRAL in the Galactic Plane (|b| < 17.5°). The current catalogue includes in total 72 hard X-ray sources detected at S/N > 4.7σ and not known to previous INTEGRAL surveys. Among them, 31 objects have also been detected in the on-going all-sky survey by the BAT telescope of the Swift observatory. For 26 sources on the list, we suggest possible identifications: 21 active galactic nuclei, two cataclysmic variables, two isolated pulsars or pulsar wind nebulae and one supernova remnant; 46 sources from the catalogue remain unclassified.

scholarly journals The Hard X‐Ray to Gamma‐Ray Spectrum in the EGRET Active Galactic Nuclei

1998 ◽  
Vol 508 (2) ◽  
pp. 601-607 ◽  
Author(s):  
Marco Fatuzzo ◽  
Fulvio Melia
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
X Ray

scholarly journals The X-ray spectral evolution and radio–X-ray correlation in radiatively efficient black-hole sources

2014 ◽  
Vol 10 (S312) ◽  
pp. 249-251
Author(s):  
Ai-Jun Dong ◽  
Qingwen Wu ◽  
Xiao-Feng Cao
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Spectral Evolution ◽  
Critical Flux ◽  
Fundamental Plane ◽  
X Ray ◽  
Data Points ◽  
X Ray Binaries

AbstractWe explore X-ray spectral evolution and radio–X-ray correlation simultaneously for four X-ray binaries (XRBs). We find that hard X-ray photon indices, Γ, are anti- and positively correlated to X-ray fluxes when the X-ray flux, F3–9keV, is below and above a critical flux, FX,crit, which may be regulated by ADAF and disk-corona respectively. We find that the data points with anti-correlation of Γ-F3–9keV follow the universal radio–X-ray correlation of FR ∝ FXb (b ~ 0.5-0.7), while the data points with positive X-ray spectral evolution follow a steeper radio–X-ray correlation (b ~ 1.4, the so-called ‘outliers track’). The bright active galactic nuclei (AGNs) share similar X-ray spectral evolution and radio–X-ray correlation as XRBs in ‘outliers’ track, and we present a new fundamental plane of log LR=1.59+0.28−0.22 log LX−0.22+0.19−0.20 log MBH−28.97+0.45−0.45 for these radiatively efficient BH sources.

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