Line emission from optically thick relativistic accretion tori

Fuerst, Steven V.; Wu, Kinwah

doi:10.1051/0004-6361:20066008

Cited by 19 publications

(16 citation statements)

References 49 publications

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“…A non-exhaustive reference list for later studies is in Ref. [138][139][140][141][142][143][144][145][146][147][148][149][150][151]. Recently, also the L-line at 0.9 keV, coming from electrons absorbed to the L-shell, has been observed [152].…”

Section: Broad Iron Lines In the X-ray Spectrummentioning

confidence: 99%

Gravitational lensing by black holes

2010

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We review the theoretical aspects of gravitational lensing by black holes, and discuss the perspectives for realistic observations. We will first treat lensing by spherically symmetric black holes, in which the formation of infinite sequences of higher order images emerges in the clearest way. We will then consider the effects of the spin of the black hole, with the formation of giant higher order caustics and multiple images. Finally, we will consider the perspectives for observations of black hole lensing, from the detection of secondary images of stellar sources and spots on the accretion disk to the interpretation of iron K-lines and direct imaging of the shadow of the black hole

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Section: Broad Iron Lines In the X-ray Spectrummentioning

confidence: 99%

Gravitational lensing by black holes

2010

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“…With this, the structure of the accretion torus can be determined by solving only the remaining hydrodynamic equations and the equation of state. For the purposes of this work we considered this phenomenological approach and constructed accretion tori assuming a specific angular velocity profile within the torus (see also Fuerst & Wu 2004, 2007 and Abramowicz (2005). With the angular velocity profile specified, we determined the density and entire flow profiles in terms of certain normalised variables.…”

Section: Modelling Accretion Torimentioning

confidence: 99%

“…following Fuerst & Wu (2004, 2007, where r k is the radius on the equatorial plane at which the material circulates with a Keplerian velocity. The differential rotational velocity gradient gives rise to an implicit pressure force, supporting the torus material above and below the equatorial plane.…”

Section: Emission Surface Of Rotationally Supported Torusmentioning

confidence: 99%

General relativistic radiative transfer: formulation and emission from structured tori around black holes

Younsi

Fuerst

2012

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We aim to construct a general relativistic radiative transfer formulation, applicable to particles with or without mass in astrophysical settings, wherein ray-tracing calculations can be performed for arbitrary geodesics for a given space-time geometry. The relativistic radiative transfer formulation is derived from first principles: conserving particle number and phase-space density. The formulation is covariant, and transfer calculations are conducted along particle geodesics connecting the emitters and the observer. The geodesics are determined through the space-time metric, which is specified beforehand. Absorption and emission in the radiative transfer calculations are treated explicitly. The particle-medium interaction is evaluated in the local inertial frame, co-moving with the medium. Relativistic, geometrical and optical depth effects are treated self-consistently within an integral covariant framework. We present a self-consistent general relativistic radiative transfer formulation with explicit treatment of emission and absorption. The formulation is general and is applicable to both particles with mass and without mass. The presence of particles has two major effects: firstly the particle bundle ray is no longer along the null geodesic, and secondly the intensity variation along the particle bundle ray is reduced by an aberration factor. The radiative transfer formulation can handle 3D geometrical settings and structured objects with variations and gradients in the optical depths across the objects and along the line-of-sight. Such scenarios are applicable in calculations of photon emission from complex structured accretion flows around black holes and neutrino emission from remnant neutron tori in neutron-star mergers. We apply the formulation and demonstrate radiation transfer calculations for emission from accretion tori around rotating black holes. We consider two cases: idealised optically thick tori that have a sharply defined emission boundary surface, and structured tori that allow variations in the absorption coefficient and emissivity within the tori. We show intensity images and emission spectra of the tori obtained in our calculations. Our findings in the radiative transfer calculations are summarised as follows. (i) Geometrical effects, such as lensing-induced self-occulation and multiple-image contribution are much more significant in accretion tori than geometrically thin accretion disks. (ii) Optically thin accretion tori show emission line profiles distinguishable from the profiles of lines from optically thick accretion tori and lines from optically thick geometrically thin accretion disks. (iii) The line profiles of the optically thin accretion tori have a weaker dependence on the viewing inclination angle than those of the optically thick accretion tori or accretion disks, especially at high viewing inclination angles. (iv) Limb effects are present in accretion tori with finite optical depths, due to density and temperature stratification within the tori. We note that in accretion ...

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“…Future VLBI observations will provide an excellent opportunity to constrain the injection site of non-thermal electrons and test the predictions of different jet origin models. For further comparison, general-relativistic radiative transfer should be included to take into account the energy shift and aberrations due to the fluid motion and the black hole's strong gravitational field (e.g., Fuerst & Wu 2004;Schnittman & Bertschinger 2004;Fuerst & Wu 2007;Dexter & Agol 2009;Vincent et al 2011;Younsi et al 2012;Chan et al 2013;Pu et al 2016).…”

Section: Discussionmentioning

confidence: 99%

Observable Emission Features of Black Hole GRMHD Jets on Event Horizon Scales

Younsi³

et al. 2017

ApJ

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The general-relativistic magnetohydrodynamical (GRMHD) formulation for black hole-powered jets naturally gives rise to a stagnation surface, wherefrom inflows and outflows along magnetic field lines that thread the black hole event horizon originate. We derive a conservative formulation for the transport of energetic electrons which are initially injected at the stagnation surface and subsequently transported along flow streamlines. With this formulation the energy spectra evolution of the electrons along the flow in the presence of radiative and adiabatic cooling is determined. For flows regulated by synchrotron radiative losses and adiabatic cooling, the effective radio emission region is found to be finite, and geometrically it is more extended along the jet central axis. Moreover, the emission from regions adjacent to the stagnation surface is expected to be the most luminous as this is where the freshly injected energetic electrons concentrate. An observable stagnation surface is thus a strong prediction of the GRMHD jet model with the prescribed non-thermal electron injection. Future millimeter/sub-millimeter (mm/sub-mm) very-long-baseline interferometric (VLBI) observations of supermassive black hole candidates, such as the one at the center of M87, can verify this GRMHD jet model and its associated non-thermal electron injection mechanism.

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Line emission from optically thick relativistic accretion tori

Cited by 19 publications

References 49 publications

Gravitational lensing by black holes

Gravitational lensing by black holes

General relativistic radiative transfer: formulation and emission from structured tori around black holes

Observable Emission Features of Black Hole GRMHD Jets on Event Horizon Scales

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