Acoustic horizons in axially symmetric relativistic accretion

Abraham, Hrvoje; Bilić, Neven; Das, Tapas K.

doi:10.1088/0264-9381/23/7/010

Cited by 46 publications

(88 citation statements)

References 43 publications

(58 reference statements)

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“…In the simplest idealized case when the disc thickness is assumed to be constant, one would expect no distinction between critical and sonic points. In this case, as has been demonstrated for a thin disc accretion onto the Kerr black hole [15], the quantity ∆r s c vanishes identically for any astrophysically relevant value of E, λ, γ, and the Kerr black-hole spin parameter a.…”

Section: F Distinction Between Critical Points and Sonic Pointssupporting

confidence: 58%

A black-hole accretion disc as an analogue gravity model

Das¹,

Bilić²,

Dasgupta³

2007

J. Cosmol. Astropart. Phys.

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We formulate and solve the equations governing the transonic behaviour of a general relativistic black-hole accretion disc with non-zero advection velocity. We demonstrate that a relativistic Rankine-Hugoniot shock may form leading to the formation of accretion powered outflow. We show that the critical points of transonic discs generally do not coincide with the corresponding sonic points. The collection of such sonic points forms an axisymmetric hypersurface, generators of which are the acoustic null geodesics, i.e. the phonon trajectories. Such a surface is shown to be identical with an acoustic event horizon. The acoustic surface gravity and the corresponding analogue horizon temperature TAH at the acoustic horizon are then computed in terms of fundamental accretion parameters. Physically, the analogue temperature is associated with the thermal phonon radiation analogous to the Hawking radiation of the black-hole horizon.Thus, an axisymmetric black-hole accretion disc is established as a natural example of the classical analogue gravity model, for which two kinds of horizon exist simultaneously. We have shown that for some values of astrophysically relevant accretion parameters, the analogue temperature exceeds the corresponding Hawking temperature. We point out that acoustic white holes can also be generated for a multi-transonic black-hole accretion with a shock. Such a white hole, produced at the shock, is always flanked by two acoustic black holes generated at the inner and the outer sonic points. Finally, we discuss possible applications of our work to other astrophysical events which may exhibit analogue effects.

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Section: F Distinction Between Critical Points and Sonic Pointssupporting

confidence: 58%

A black-hole accretion disc as an analogue gravity model

Das¹,

Bilić²,

Dasgupta³

2007

J. Cosmol. Astropart. Phys.

Self Cite

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“…(50) and (55) it is evident that the metric elements of the acoustic metric are time independent and hence the acoustic spacetime is stationary. In analogy to the general relativity, therefore, we can define the acoustic horizon as a time-like hypersurface whose normal n µ is null with respect to the acoustic metric [51,52] …”

Section: Location Of the Acoustic Horizonmentioning

confidence: 99%

Relativistic sonic geometry for isothermal accretion in the Schwarzschild metric

Shaikh

Firdousi

Das

2017

Class. Quantum Grav.

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Abstract. In this work, we perform linear perturbation on general relativistic isothermal accretion onto a non-rotating astrophysical black hole to study the salient features of the corresponding emergent acoustic metric. For spherically symmetric accretion as well as for the axially symmetric matter flow for three different geometric configuration of matter, we perturb the velocity potential, the mass accretion rate, and the integral solution of the time independent part of the general relativistic Euler equation to obtain such acoustic geometry. We provide the procedure to locate the acoustic horizon and identify such horizon with the transonic surfaces of the accreting matter through the construction of the corresponding causal structures. We then discuss how one can compute the value of the acoustic surface gravity in terms of the accretion variable corresponding to the background flow solutions -i.e., stationary integral transonic accretion solutions for different matter geometries. We show that the salient features of the acoustic geometry is independent of the physical variable we perturb, but sensitively depends on the geometric configuration of the black hole accretion disc.

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“…This will help in studying the low angular momentum pseudo-Schwarzschild axisymmetric black hole accretion as a natural example of analogue gravity phenomena. It has recently been shown that the analogue surface gravity can be computed for multi-critical accretion onto astrophysical black holes (Abraham et al 2006;Das et al 2007). The present work will allow to study such phenomena for various different geometric configuration of the flow.…”

Section: Discussionmentioning

confidence: 99%

The role of flow geometry in influencing the stability criteria for low angular momentum axisymmetric black hole accretion

et al. 2012

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Using mathematical formalism borrowed from dynamical systems theory, a complete analytical investigation of the critical behaviour of the stationary flow configuration for the low angular momentum axisymmetric black hole accretion provides valuable insights about the nature of the phase trajectories corresponding to the transonic accretion in the steady state, without taking recourse to the explicit numerical solution commonly performed in the literature to study the multi-transonic black hole accretion disc and related astrophysical phenomena. Investigation of the accretion flow around a non rotating black hole under the influence of various pseudo-Schwarzschild potentials and forming different geometric configurations of the flow structure manifests that the general profile of the parameter space divisions describing the multi-critical accretion is roughly equivalent for various flow geometries. However, a mere variation of the polytropic index of the flow cannot map a critical solution from one flow geometry to the another, since the numerical domain of the parameter space responsible to produce multi-critical accretion does not undergo a continuous transformation in multi-dimensional parameter space. The stationary configuration used to demonstrate the aforementioned findings is shown to be stable under linear perturbation for all kind of flow geometries, black hole potentials, and the corresponding equations of state used to obtain the critical transonic solutions. Finally, the structure of the acoustic metric corresponding to the propagation of the linear perturbation studied are discussed for various flow geometries used.

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Acoustic horizons in axially symmetric relativistic accretion

Cited by 46 publications

References 43 publications

A black-hole accretion disc as an analogue gravity model

A black-hole accretion disc as an analogue gravity model

Relativistic sonic geometry for isothermal accretion in the Schwarzschild metric

The role of flow geometry in influencing the stability criteria for low angular momentum axisymmetric black hole accretion

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