scholarly journals Relativistic Particle Transport in Hot Accretion Disks

1994 ◽  
Vol 142 ◽  
pp. 949-953
Author(s):  
Peter A. Becker ◽  
Menas Kafatos ◽  
Michael Maisack
Keyword(s):  
Black Holes ◽  
Accretion Disks ◽  
Relativistic Particle ◽  
High Energy ◽  
Black Hole Mass ◽  
Radiation Mechanisms ◽  
Accretion Rates ◽  
Inner Region ◽  
Two Temperature ◽  
Intense Radiation

AbstractAccretion disks around rapidly rotating black holes provide one of the few plausible models for the production of intense radiation in AGNs above energies of several hundred MeV. The rapid rotation of the hole increases the binding energy per nucleon in the last stable orbit relative to the Schwarzschild case, and naturally leads to ion temperatures in the range 1012 -1013 K for sub-Eddington accretion rates. The protons in the hot inner region of a steady, two-temperature disk form a reservoir of energy that is sufficient to power the observed EGRET outbursts if the black hole mass is 1010M⊙ . Moreover, the accretion timescale for the inner region is comparable to the observed transient timescale of ~1 week. Hence EGRET outbursts may be driven by instabilities in hot, two-temperature disks around supermassive black holes. In this paper we discuss turbulent (stochastic) acceleration in hot disks as a possible source of GeV particles and radiation. We constrain the model by assuming the turbulence is powered by a collective instability that drains energy from the hot protons. We also provide some ideas concerning new, high-energy Penrose processes that produce GeV emission be directly tapping the rotational energy of Kerr black holes.Subject headings: acceleration of particles — accretion, accretion disks — galaxies: nuclei — quasars: individual (3C 279) — radiation mechanisms: nonthermal

scholarly journals Hot Accretion Disks with Magnetic Field and Thermal Cyclo-Synchrotron Radiation

1994 ◽  
Vol 159 ◽  
pp. 485-485
Author(s):  
Masaaki Kusunose ◽  
Andrzej A. Zdziarski
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Spectral Index ◽  
Accretion Disks ◽  
Qualitative Properties ◽  
Bremsstrahlung Radiation ◽  
X Ray ◽  
Accretion Rates ◽  
Galactic Black Hole ◽  
Two Temperature

We study the structure of hot, two-temperature accretion disks around black holes, including the effects of thermal cyclo-synchrotron radiation and magnetic viscosity. This work is an extension of previous work by Björnsson & Svensson (1991a, b, 1992) and Kusunose & Mineshige (1992), which did not include those effects. Magnetic field, B, is assumed to be randomly oriented and determined by prescribing the ratio α = Pmag/Pgas or α = Pmag/(Pgas + Prad), where Pmag, Pgas, and Prad are the pressures of magnetic field, gas, and radiation, respectively. We find those effects do not change the qualitative properties of the disks, i.e., there are two critical accretion rates related to production of e± pairs, ṀcrU and ṀcrL that affect the number of local and global disk solutions, as recently found for the case with B = 0 (Björnsson & Svensson 1991a, b, 1992). However, a critical value of the α-viscosity parameter above which those critical accretion rates disappear becomes smaller than αcr = 1 found in the case of B = 0, for Pmag = α(Pgas + Prad). If Pmag = αPgas, on the other hand, αcr is still about unity. Moreover, when Comptonized cyclo-synchrotron radiation dominates Comptonized bremsstrahlung, radiation from the disk obeys a power law with the energy spectral index of ∼ 0.5, in a qualitative agreement with X-ray observations of AGNs and Galactic black hole candidates. The spectral index is weakly dependent on the mass accretion rate.

scholarly journals Alignment of Magnetized Accretion Disks and Relativistic Jets with Spinning Black Holes

Science ◽  
2012 ◽  
Vol 339 (6115) ◽  
pp. 49-52 ◽  
Author(s):  
Jonathan C. McKinney ◽  
Alexander Tchekhovskoy ◽  
Roger D. Blandford
Keyword(s):  
Black Holes ◽  
Accretion Disks ◽  
Three Dimensional ◽  
Host Galaxies ◽  
Relativistic Jets ◽  
Outer Disk ◽  
Alignment Mechanism ◽  
General Relativistic ◽  
Thin Disks ◽  
Intense Radiation

Accreting black holes (BHs) produce intense radiation and powerful relativistic jets, which are affected by the BH’s spin magnitude and direction. Although thin disks might align with the BH spin axis via the Bardeen-Petterson effect, this does not apply to jet systems with thick disks. We used fully three-dimensional general relativistic magnetohydrodynamical simulations to study accreting BHs with various spin vectors and disk thicknesses and with magnetic flux reaching saturation. Our simulations reveal a “magneto-spin alignment” mechanism that causes magnetized disks and jets to align with the BH spin near BHs and to reorient with the outer disk farther away. This mechanism has implications for the evolution of BH mass and spin, BH feedback on host galaxies, and resolved BH images for the accreting BHs in SgrA* and M87.

scholarly journals Hybrid Accretion-Disks in AGN and the AGN Contribution to the XRB

1994 ◽  
Vol 159 ◽  
pp. 491-491
Author(s):  
Amri Wandel
Keyword(s):  
Accretion Disk ◽  
Accretion Disks ◽  
Power Law ◽  
Accretion Rate ◽  
Bremsstrahlung Spectrum ◽  
Spectral Evolution ◽  
X Ray ◽  
X Ray Background ◽  
Inner Region ◽  
Two Temperature

The hybrid accretion-disk (HAD) model links the two characteristic components of AGN spectra – the UV bump and the X-ray power-law – in the framework of one physical model. The radially stratified hybrid disk is a self consistent combination of a thin, cool accretion disk at large radii, with an inner hot two-temperature disk. Its spectrum consists of three components, corresponding to the three radial disk regions: a blackbody thermal spectrum from the outer cool disk, a Comptonized soft photon power-law spectrum from the intermediate region, and a thermal Comptonized bremsstrahlung spectrum from the inner region. The dependence of the hybrid disk spectrum on the accretion rate and on other parameters is discussed and applied to AGN spectral evolution, and in particular to explaining the cosmic X-ray background by AGN.

scholarly journals Transition from radiatively inefficient to cooling dominated phase in two temperature accretion disks around black holes

2009 ◽  
Vol 9 (12) ◽  
pp. 1331-1342 ◽  
Author(s):  
Monika Sinha ◽  
S. R Rajesh ◽  
Banibrata Mukhopadhyay
Keyword(s):  
Black Holes ◽  
Accretion Disks ◽  
Two Temperature

scholarly journals AGN and Host Galaxies in the COSMOS Survey

2010 ◽  
Vol 6 (S277) ◽  
pp. 21-25
Author(s):  
Christopher D. Impey ◽  
Jonathan R. Trump ◽  
Jared M. Gabor ◽  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Supermassive Black Holes ◽  
Black Hole Mass ◽  
Host Galaxies ◽  
Intermediate Mass ◽  
Evolution Of Galaxies ◽  
Accretion Rates ◽  
Deep Survey ◽  
Optical Surveys

AbstractThe Cosmological Evolution Survey (COSMOS) is a unique tool for studying low level AGN activity and the co-evolution of galaxies and supermassive black holes. COSMOS involves the largest contiguous region of the sky ever imaged by HST; it includes very complete multiwavelength coverage, and the largest joint samples of galaxy and AGN redshifts in any deep survey. The result is a search for AGN with low black hole mass, low accretion rates, and levels of obscuration that can remove them from optical surveys. A complete census of intermediate mass black holes at redshifts of 1 to 3 is required to tell the story of the co-evolution of galaxies and their embedded, and episodically active, black holes.

scholarly journals Influence of Cosmic Repulsion and Magnetic Fields on Accretion Disks Rotating around Kerr Black Holes

Universe ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. 26 ◽  
Author(s):  
Zdeněk Stuchlík ◽  
Martin Kološ ◽  
Jiří Kovář ◽  
Petr Slaný ◽  
Arman Tursunov
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Magnetic Fields ◽  
Accretion Disks ◽  
Vacuum Energy ◽  
High Energy ◽  
Supermassive Black Holes ◽  
Ultra High Energy ◽  
Thin And Thick Disks ◽  
High Energy Particles

We present a review of the influence of cosmic repulsion and external magnetic fields on accretion disks rotating around rotating black holes and on jets associated with these rotating configurations. We consider both geometrically thin and thick disks. We show that the vacuum energy represented by the relic cosmological constant strongly limits extension of the accretion disks that is for supermassive black holes comparable to extension of largest galaxies, and supports collimation of jets at large distances from the black hole. We further demonstrate that an external magnetic field crucially influences the fate of ionized Keplerian disks causing creation of winds and jets, enabling simultaneously acceleration of ultra-high energy particles with energy up to 10 21 eV around supermassive black holes with M ∼ 10 10 M ⊙ surrounded by sufficiently strong magnetic field with B ∼ 10 4 G. We also show that the external magnetic fields enable existence of “levitating” off-equatorial clouds or tori, along with the standard equatorial toroidal structures, if these carry a non-vanishing, appropriately distributed electric charge.

scholarly journals Two-Temperature Transonic Accretion Disks

1998 ◽  
Vol 188 ◽  
pp. 411-411
Author(s):  
K.E. Nakamura ◽  
M. Kusunose ◽  
R. Matsumoto ◽  
S. Kato
Keyword(s):  
Accretion Disks ◽  
Thermal Structure ◽  
Electron System ◽  
High Energy ◽  
Ion Energy ◽  
X Ray ◽  
Accretion Flows ◽  
High Energy Emission ◽  
Advective Heat Transport ◽  
Two Temperature

The optically thin, advection-dominated accretion flows are thermally stable against global perturbations. In addition, they have high temperatures because of inefficient radiative cooling. They are thus promising candidates of models to explain the high energy emission of X-ray stars and AGNs. So far, models, however, take no account of the advective heat transport in determining the thermal structure of the electron system. The validly of this neglect, however, must be checked by integrating the electron energy equation globally as well as the ion energy one.

High energy radiation from jets and accretion disks near rotating black holes

2017 ◽  
Author(s):  
Michael O’Riordan ◽  
Asaf Pe’er ◽  
Jonathan C. McKinney
Keyword(s):  
Black Holes ◽  
Accretion Disks ◽  
High Energy ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Rotating Black Holes

scholarly journals Radiatively inefficient accretion disks in low-luminosity AGN†

2006 ◽  
Vol 2 (S238) ◽  
pp. 273-276 ◽  
Author(s):  
Ferdinando D. Macchetto ◽  
Marco Chiaberge
Keyword(s):  
Black Hole ◽  
Accretion Disks ◽  
Hubble Space Telescope ◽  
Seyfert Galaxies ◽  
Radio Galaxies ◽  
Black Hole Mass ◽  
Limited Sample ◽  
Radiative Efficiency ◽  
Accretion Rates ◽  
Black Hole Masses

AbstractWe study a complete and distance-limited sample of 25 LINERs, 21 of which have been imaged with the Hubble Space Telescope to study their physical properties and to compare their radio and optical properties with those of other samples of local AGNs, namely Seyfert galaxies and low-luminosity radio galaxies (LLRG). Our results show that the LINERs population is not homogeneous, as there are two subclasses: i) the first class is similar to LLRG, as it extends the population of radio-loud nuclei to lower luminosities; ii) the second is similar to Seyferts, and extends the properties of radio-quiet nuclei towards the lowest luminosities. The different nature of the various classes of local AGN are best understood when the fraction of the Eddington luminosity they irradiate, Lo/LEdd, is plotted against the nuclear radio-loudness parameter: Seyferts are associated with relatively high radiative efficiencies Lo/LEdd ≳ 104 (and high accretion rates onto low mass black holes); LLRG are associated with low radiative efficiencies (and low accretion rates onto high black hole masses); all LINERs have low radiative efficiency (and accretion rates), and can be radio-loud or radio quiet depending on their black hole mass.

scholarly journals Planck Neutrinos as Ultra High Energy Cosmic Rays

2020 ◽  
Vol 29 (1) ◽  
pp. 40-46
Author(s):  
Dmitri L. Khokhlov
Keyword(s):  
Black Holes ◽  
Cosmic Rays ◽  
Standard Model ◽  
Active Galactic Nuclei ◽  
Planck Scale ◽  
Galactic Nuclei ◽  
High Energy ◽  
Ultra High Energy ◽  
High Energy Cosmic Rays ◽  
The Standard Model

AbstractThe studied conjecture is that ultra high energy cosmic rays (UHECRs) are hypothetical Planck neutrinos arising in the decay of the protons falling onto the gravastar. The proton is assumed to decay at the Planck scale into positron and four Planck neutrinos. The supermassive black holes inside active galactic nuclei, while interpreted as gravastars, are considered as UHECR sources. The scattering of the Planck neutrinos by the proton at the Planck scale is considered. The Planck neutrinos contribution to the CR events may explain the CR spectrum from 5 × 1018 eV to 1020 eV. The muon number in the Planck neutrinos-initiated shower is estimated to be larger by a factor of 3/2 in comparison with the standard model that is consistent with the observational data.

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