scholarly journals Advective Disks

1997 ◽  
Vol 163 ◽  
pp. 75-89 ◽  
Author(s):  
R. Narayan
Keyword(s):  
Black Holes ◽  
Recent Work ◽  
Galactic Nuclei ◽  
Critical Value ◽  
Event Horizons ◽  
X Ray ◽  
Accretion Flows ◽  
Accretion Rates ◽  
X Ray Binaries ◽  
Spectral States

AbstractRecent work on advection-dominated accretion flows (ADAFs) is reviewed. The article concentrates on an optically thin branch of ADAFs which is present at mass accretion rates below a critical value ~ (10−2– 10−1) the Eddington rate. Models based on this branch have been quite successful at explaining a number of low-luminosity X-ray binaries and galactic nuclei, and some brighter systems. Some progress has also been made toward understanding the various spectral states of accreting black holes. It is argued that ADAFs may provide one of the best techniques for demonstrating the reality of event horizons in black holes.

scholarly journals Radiative efficiency of hot accretion flow and the radio/X-ray correlation in X-ray binaries

2014 ◽  
Vol 10 (S312) ◽  
pp. 139-140
Author(s):  
Fu-Guo Xie
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Accretion Rate ◽  
Galactic Nuclei ◽  
X Ray ◽  
Radiative Efficiency ◽  
Accretion Flow ◽  
Accretion Rates ◽  
Distinctive Property ◽  
X Ray Binaries

AbstractSignificant progresses have been made since the discovery of hot accretion flow, a theory successfully applied to the low-luminosity active galactic nuclei (LLAGNs) and black hole (BH) X-ray binaries (BHBs) in their hard states. Motivated by these updates, we re-investigate the radiative efficiency of hot accretion flow. We find that, the brightest regime of hot accretion flow shows a distinctive property, i.e. it has a constant efficiency independent of accretion rates, similar to the standard thin disk. For less bright regime, the efficiency has a steep positive correlation with the accretion rate, while for faint regime typical of advection-dominated accretion flow, the correlation is shadower. This result can naturally explain the observed two distinctive correlations between radio and X-ray luminosities in black hole X-ray binaries. The key difference in systems with distinctive correlations could be the viscous parameter, which determines the critical luminosity of different accretion modes.

scholarly journals Non-axisymmetric Instabilities in Shocked Accretion Flows

2003 ◽  
Vol 214 ◽  
pp. 95-96
Author(s):  
Wei-Min Gu ◽  
Thierry Foglizzo
Keyword(s):  
Black Hole ◽  
Numerical Integration ◽  
Recent Work ◽  
Growth Rates ◽  
Linearized Equations ◽  
X Ray ◽  
Accretion Flows ◽  
The Stability ◽  
X Ray Binaries ◽  
Axisymmetric Perturbations

We investigate the stability of shocked inviscid isothermal accretion flows onto a black hole. Of the two possible shock positions, the outer one is known to be stable to axisymmetric perturbations, while the inner one is unstable. Our recent work, however, shows that the outer shock is generally linearly unstable to non-axisymmetric perturbations. Eigenmodes and growth rates are obtained by numerical integration of the linearized equations. These results offer new perspectives to interpret the variability of X-ray binaries.

scholarly journals A public relativistic transfer function model for X-ray reverberation mapping of accreting black holes

2019 ◽  
Vol 488 (1) ◽  
pp. 324-347 ◽  
Author(s):  
Adam Ingram ◽  
Guglielmo Mastroserio ◽  
Thomas Dauser ◽  
Pieter Hovenkamp ◽  
Michiel van der Klis ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Radial Profile ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Geometric Constraints ◽  
Time Lags ◽  
X Ray ◽  
X Ray Binaries

ABSTRACTWe present the publicly available model reltrans that calculates the light-crossing delays and energy shifts experienced by X-ray photons originally emitted close to the black hole when they reflect from the accretion disc and are scattered into our line of sight, accounting for all general relativistic effects. Our model is fast and flexible enough to be simultaneously fit to the observed energy-dependent cross-spectrum for a large range of Fourier frequencies, as well as to the time-averaged spectrum. This not only enables better geometric constraints than only modelling the relativistically broadened reflection features in the time-averaged spectrum, but additionally enables constraints on the mass of supermassive black holes in active galactic nuclei and stellar-mass black holes in X-ray binaries. We include a self-consistently calculated radial profile of the disc ionization parameter and properly account for the effect that the telescope response has on the predicted time lags. We find that a number of previous spectral analyses have measured artificially low source heights due to not accounting for the former effect and that timing analyses have been affected by the latter. In particular, the magnitude of the soft lags in active galactic nuclei may have been underestimated, and the magnitude of lags attributed to thermal reverberation in X-ray binaries may have been overestimated. We fit reltrans to the lag-energy spectrum of the Seyfert galaxy Mrk 335, resulting in a best-fitting black hole mass that is smaller than previous optical reverberation measurements (∼7 million compared with ∼14–26 million M⊙).

scholarly journals LIGO tells us LINERs are not optically thick RIAFs

2019 ◽  
Vol 490 (1) ◽  
pp. L42-L46 ◽  
Author(s):  
K E Saavik Ford ◽  
B McKernan
Keyword(s):  
Black Holes ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Scale Height ◽  
Gas Flows ◽  
Local Universe ◽  
Accretion Flows ◽  
Upper Limits ◽  
Accretion Rates

ABSTRACT Low ionization nuclear emission-line regions (LINERs) are a heterogeneous collection of up to one-third of galactic nuclei in the local Universe. It is unclear whether LINERs are simply the result of low accretion rates onto supermassive black holes (BHs) or whether they include a large number of optically thick radiatively inefficient but super-Eddington accretion flows (RIAFs). Optically thick RIAFs are typically discs of large-scale height or quasi-spherical gas flows. These should be dense enough to trap and merge a large number of the stellar mass BHs, which we expect to exist in galactic nuclei. Electromagnetic observations of photospheres of accretion flows do not allow us to break model degeneracies. However, gravitational wave observations probe the interior of accretion flows where the merger of stellar mass BHs can be greatly accelerated over the field rate. Here, we show that the upper limits on the rate of BH mergers observed with LIGO demonstrate that most LINERs cannot be optically thick RIAFs.

scholarly journals Coupling of the accretion disk and corona around black holes

2012 ◽  
Vol 8 (S290) ◽  
pp. 62-65
Author(s):  
B. F. Liu
Keyword(s):  
Black Holes ◽  
Complete Removal ◽  
Thin Disk ◽  
Inverse Compton Scattering ◽  
Accretion Flows ◽  
Viscous Heat ◽  
Inverse Compton ◽  
Accretion Rates ◽  
Hot Corona ◽  
Spectral States

AbstractThe interaction between a hot corona and a cold thin disk can drive cold gas evaporating into the corona or hot gas condensing into the thin disk. The evaporation is caused by heat conduction downwards to the disk; while condensation is caused by overcooling of corona gas through inverse Compton scattering. Evaporation occurs at low accretion rates when the corona cannot efficiently radiate the viscous heat, thereby part of which is conducted down and heats up gas. Condensation occurs at high accretion rates when the Compton cooling of disk photons is strong enough to efficiently cool the corona gas. An important consequence of the evaporation is complete removal of the disk at a certain distances. In contrast, condensation can lead to a weak corona or complete collapse of the corona. This causes the observed transitions between various spectral states, at which the accretion flows are dominated respectively by ADAF, disk+ corona, and thin disk from low to high accretion rates, providing a natural explanation to the low, intermediate and high spectral states in BHXRBs, as well as their transitions. The same process can also be applied to accretion around supermassive black holes.

scholarly journals Black Holes in Galactic Nuclei, X-Ray Binaries and Ultraluminous X-Ray Sources

2005 ◽  
Vol 22 (3) ◽  
pp. 195-198 ◽  
Author(s):  
Zdenka Kuncic
Keyword(s):  
Black Holes ◽  
Galactic Nuclei ◽  
Stellar Mass ◽  
Supermassive Black Holes ◽  
Intermediate Mass ◽  
X Ray ◽  
Gravitational Influence ◽  
X Ray Binaries ◽  
Intermediate Mass Black Holes

AbstractThis review summarizes the astrophysical evidence for the existence of black holes provided by their gravitational influence on nearby matter. Two classes of accreting black holes have now been observationally verified: supermassive black holes (SMBHs) in galactic nuclei, and stellar-mass black holes in X-ray binaries (XRBs). With the recent re-discovery of ultra-luminous X-ray (ULX) sources, fresh evidence has also emerged for the existence of a third class of accreting black holes: intermediate-mass black holes (IMBHs). The properties of the three classes of accreting black holes are briefly discussed.

Internal Energy of the Non-Spinning Black Holes

2013 ◽  
Vol 787 ◽  
pp. 681-686
Author(s):  
Di Po Mahto ◽  
Rama Nand Mehta ◽  
Umakant Prasad ◽  
Krishna Murari Singh ◽  
Mirza Sarfaraz Hussain John
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Internal Energy ◽  
Galactic Nuclei ◽  
Black Hole Thermodynamics ◽  
X Ray ◽  
X Ray Binaries

The present paper derives an expression for internal energy of the Non-spinning black holes using first law of black hole thermodynamics and calculates their values of different test Non-spinning holes existing in X-ray binaries (XRBs) and Active Galactic Nuclei (AGN).

Polarization Variability of Active Galactic Nuclei and X‐Ray Binaries

1997 ◽  
Vol 487 (1) ◽  
pp. 142-152 ◽  
Author(s):  
Gang Bao ◽  
Petr Hadrava ◽  
Paul J. Wiita ◽  
Ying Xiong
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
X Ray ◽  
X Ray Binaries

scholarly journals X-ray properties of He ii λ 1640 emitting galaxies in VANDELS

2020 ◽  
Vol 496 (3) ◽  
pp. 3796-3807
Author(s):  
A Saxena ◽  
L Pentericci ◽  
D Schaerer ◽  
R Schneider ◽  
R Amorin ◽  
...  
Keyword(s):  
Formation Rate ◽  
Galactic Nuclei ◽  
X Ray ◽  
Star Forming ◽  
Set Constraints ◽  
Significant Difference ◽  
Low Metallicity ◽  
Matched Samples ◽  
X Ray Binaries

ABSTRACT We explore X-ray emission from a sample of 18 He ii λ1640 emitting star-forming galaxies at z ∼ 2.3–3.6 from the VANDELS survey in the Chandra Deep Field South, to set constraints on the role of X-ray sources in powering the He ii emission. We find that 4 He ii emitters have tentative detections with S/N ∼ 2 and have X-ray luminosities, LX = 1.5−4.9 × 1041 erg s−1. The stacked luminosity of all 18 He ii emitters is 2.6 × 1041 erg s−1, and that of a subset of 13 narrow He ii emitters (FHWM(He ii) < 1000 km s−1) is 3.1 × 1041 erg s−1. We also measure stacked LX for non-He ii emitters through bootstrapping of matched samples, and find LX = 2.5 × 1041 erg s−1, which is not significantly different from LX measured for He ii emitters. The LX per star formation rate for He ii emitters (log (LX/SFR) ∼ 40.0) and non-emitters (log (LX/SFR) ∼ 39.9) are also comparable and in line with the redshift evolution and metallicity dependence predicted by models. Due to the non-significant difference between the X-ray emission from galaxies with and without He ii, we conclude that X-ray binaries or weak or obscured active galactic nuclei are unlikely to be the dominant producers of He ii ionizing photons in VANDELS star-forming galaxies at z ∼ 3. Given the comparable physical properties of both He ii emitters and non-emitters reported previously, alternative He ii ionizing mechanisms such as localized low-metallicity stellar populations, Pop-III stars, etc. may need to be explored.

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