scholarly journals Gamma-Ray Astrophysics in the Time Domain

Galaxies ◽  
2019 ◽  
Vol 7 (1) ◽  
pp. 28 ◽  
Author(s):  
Frank Rieger
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Time Domain ◽  
Gamma Ray ◽  
Black Hole Physics ◽  
Galactic Nuclei ◽  
Statistical Tools ◽  
Gamma Ray Astronomy ◽  
The Time Domain

The last few years have seen gamma-ray astronomy maturing and advancing in the field of time-domain astronomy, utilizing source variability on timescales over many orders of magnitudes, from a decade down to a few minutes and shorter, depending on the source. This review focuses on some of the key science issues and conceptual developments concerning the timing characteristics of active galactic nuclei (AGN) at gamma-ray energies. It highlights the relevance of adequate statistical tools and illustrates that the developments in the gamma-ray domain bear the potential to fundamentally deepen our understanding of the nature of the emitting source and the link between accretion dynamics, black hole physics, and jet ejection.

scholarly journals HIGH-ENERGY EMISSION FROM JET–CLOUD INTERACTIONS IN AGNs

2010 ◽  
Vol 19 (06) ◽  
pp. 931-936 ◽  
Author(s):  
ANABELLA T. ARAUDO ◽  
VALENTÍ BOSCH-RAMON ◽  
GUSTAVO E. ROMERO
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Small Region ◽  
High Energy ◽  
Energy Emission ◽  
Central Regions ◽  
High Energy Emission

Active galactic nuclei present continuum and line emission. The emission lines are originated by gas located close to the central supermassive black hole. Some of these lines are broad, and would be produced in a small region called broad-line region. This region could be formed by clouds surrounding the central black hole. In this work, we study the interaction of such clouds with the base of the jets in active galactic nuclei, and we compute the produced high-energy emission. We focus on sources with low luminosities in the inner jet regions, to avoid strong gamma-ray absorption. We find that the resulting high-energy radiation may be significant in Centaurus A. Also, this phenomenon might be behind the variable gamma-ray emission detected in M87, if very large dark clouds are present. The detection of jet–cloud interactions in active galactic nuclei would give information on the properties of the jet base and the very central regions.

scholarly journals Variability in Active Galactic Nuclei

2011 ◽  
Vol 7 (S285) ◽  
pp. 109-110
Author(s):  
Erin Wells Bonning
Keyword(s):  
Active Galactic Nuclei ◽  
Time Domain ◽  
Galactic Nuclei ◽  
Periodic Oscillation ◽  
Theoretical Models ◽  
Quasi Periodic Oscillation ◽  
Complex Processes ◽  
Central Engine ◽  
The Rich ◽  
The Time Domain

AbstractThis talk explored variability in active galactic nuclei (AGN) for a variety of scales across the time domain. From billion-year-scale intermittency to a quasi-periodic oscillation signal with a period of one hour, time-varying signals offer insights into a myriad of complex processes driven by the AGN central engine. Athough the era of time-domain observations of AGN across the spectrum has but just begun, already observations reveal the rich detail of phenomena associated with actively accreting black holes which challenge theoretical models.

scholarly journals Radio Galaxies at VHE Energies

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 116 ◽  
Author(s):  
Frank Rieger ◽  
Amir Levinson
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Concise Overview ◽  
Recent Developments ◽  
Γ Ray ◽  
Very High

Radio Galaxies have by now emerged as a new γ-ray emitting source class on the extragalactic sky. Given their remarkable observed characteristics, such as unusual gamma-ray spectra or ultrafast VHE variability, they represent unique examples to probe the nature and physics of active galactic nuclei (AGN) in general. This review provides a compact summary of their observed characteristics at very high γ-ray energies (VHE; greater than 100 GeV) along with a discussion of their possible physics implications. A particular focus is given to a concise overview of fundamental concepts concerning the origin of variable VHE emission, including recent developments in black hole gap physics.

GROUND-BASED GAMMA-RAY ASTRONOMY

2005 ◽  
Vol 20 (29) ◽  
pp. 6981-6990
Author(s):  
ADRIAN BILAND
Keyword(s):  
Active Galactic Nuclei ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Gamma Ray Astronomy ◽  
Very High Energy ◽  
Energy Gamma ◽  
New Generation ◽  
Very High

Very High Energy Gamma-Ray Astronomy (the measurement of γ above 10 GeV) is a rather young but fast evolving field. In the past 16 years some 20 sources have been discovered, about half of them are firmly established and seen with high significance by more than one experiment. This rather short list already contains very different objects like plerions, supernova remnants and active galactic nuclei. A new generation of instruments (CANGAROO III, HESS, MAGIC, VERITAS) is just starting to take data, and first preliminary results show that the sensitivity is improved by at least a factor of 100. Already during commissioning, some new sources have been discovered. This overview will summarize the techniques used in VHE gamma-ray observations as well discuss briefly some physics topics that can be investigated in this energy range.

BLACK HOLES IN GAMMA RAY BURSTS AND GALACTIC NUCLEI

2013 ◽  
Vol 22 (11) ◽  
pp. 1360008 ◽  
Author(s):  
REMO RUFFINI ◽  
C. R. ARGÜELLES ◽  
B. M. O. FRAGA ◽  
A. GERALICO ◽  
H. QUEVEDO ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Future Research ◽  
Galactic Halos ◽  
Unified Approach ◽  
Massive Black Holes ◽  
The Moment

Current research marks a clear success in identifying the moment of formation of a Black Hole of ~ 10M⊙, with the emission of a Gamma Ray Burst. This explains in terms of the 'Blackholic Energy' the source of the energy of these astrophysical systems. Their energetics up to 1054 erg, make them detectable all over our Universe. Concurrently a new problematic has been arising related to: (a) The evidence of Dark Matter in galactic halos; (b) The origin of the Super Massive Black Holes in active galactic nuclei and Quasars and (c) The purported existence of a Black Hole in the Center of our Galaxy. These three aspects of this new problematic have been traditionally approached independently. We propose an unified approach to all three of them based on a system of massive self-gravitating neutrinos in General Relativity. Perspectives of future research are presented.

scholarly journals The quantum emission of an alive black hole

2021 ◽  
pp. 2141003
Author(s):  
J. A. Rueda ◽  
R. Ruffini
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Kerr Black Hole ◽  
Galactic Nuclei ◽  
New Physics ◽  
Rotational Energy ◽  
Gamma Ray Bursts ◽  
Astrophysical Objects

A long march of 50 years of successive theoretical progress and new physics discovered using observations of gamma-ray bursts has finally led to the formulation of an efficient mechanism able to extract the rotational energy of a Kerr black hole to power these most energetic astrophysical sources and active galactic nuclei. We here present the salient features of this long-sought mechanism, based on gravito-electrodynamics, and which represents an authentic shift of paradigm of black holes as forever “alive” astrophysical objects.

scholarly journals Epicyclic Oscillations around Simpson–Visser Regular Black Holes and Wormholes

Universe ◽  
2021 ◽  
Vol 7 (8) ◽  
pp. 279
Author(s):  
Zdeněk Stuchlík ◽  
Jaroslav Vrba
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Observational Data ◽  
High Frequency ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Periodic Oscillations ◽  
High Length ◽  
Circular Geodesic

We study epicyclic oscillatory motion along circular geodesics of the Simpson–Visser meta-geometry describing in a unique way regular black-bounce black holes and reflection-symmetric wormholes by using a length parameter l. We give the frequencies of the orbital and epicyclic motion in a Keplerian disc with inner edge at the innermost circular geodesic located above the black hole outer horizon or on the our side of the wormhole. We use these frequencies in the epicyclic resonance version of the so-called geodesic models of high-frequency quasi-periodic oscillations (HF QPOs) observed in microquasars and around supermassive black holes in active galactic nuclei to test the ability of this meta-geometry to improve the fitting of HF QPOs observational data from the surrounding of supermassive black holes. We demonstrate that this is really possible for wormholes with sufficiently high length parameter l.

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