Numerical fits to important rates in high temperature astrophysical plasmas

Stepney, Susan; Guilbert, P. W.

doi:10.1093/mnras/204.4.1269

Cited by 175 publications

(179 citation statements)

References 1 publication

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“…The pseudo-Newtonian potential is adopted in the momentum equation. q ei , q br and qsyn are the energy transfer rate from ions to electrons by Coulomb collisions, the cooling rate of electrons by electron-ion and electron-electron bremsstrahlungs and the synchrotron cooling rate, respectively (Esin et al 1996;Narayan & Yi 1995;Stepney & Guilbert 1983). In calculation of qsyn, we give the magnetic field B at each radius, assuming that the ratio β of the magnetic energy density to the thermal energy density is constant throughout the region.…”

Section: Basic Equationsmentioning

confidence: 99%

Unstable mass-outflows in geometrically thick accretion flows around black holes

Okuda¹,

Das

2015

Mon. Not. R. Astron. Soc.

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Accretion flows around black holes generally result in mass-outflows that exhibit irregular behavior quite often. Using 2D time-dependent hydrodynamical calculations, we show that the mass-outflow is unstable in the cases of thick accretion flows such as the low angular momentum accretion flow and the advection-dominated accretion flow. For the low angular momentum flow, the inward accreting matter on the equatorial plane interacts with the outflowing gas along the rotational axis and the centrifugally supported oblique shock is formed at the interface of both the flows, when the viscosity parameter α is as small as α 10 −3 . The hot and rarefied blobs, which result in the eruptive mass-outflow, are generated in the inner shocked region and grow up toward the outer boundary. The advection-dominated accretion flow attains finally in the form of a torus disc with the inner edge of the disc at 3R g r 6R g and the center at 6R g r 10R g , and a series of hot blobs is intermittently formed near the inner edge of the torus and grows up along the outer surface of the torus. As a result, the luminosity and the mass-outflow rate are modulated irregularly where the luminosity is enhanced by 10−40% and the mass-outflow rate is increaed by a factor of few up to ten. We interpret the unstable nature of the outflow to be due to the KelvinHelmholtz instability, examining the Richardson number for the Kelvin-Helmholtz criterion in the inner region of the flow. We propose that the flare phenomena of Sgr A* may be induced by the unstable mass-outflow as is found in this work.

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Section: Basic Equationsmentioning

confidence: 99%

Unstable mass-outflows in geometrically thick accretion flows around black holes

Okuda¹,

Das

2015

Mon. Not. R. Astron. Soc.

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“…Following Stepney & Guilbert (1983), where the z-axis is chosen to be parallel to the sum of the initial electron momenta, we rewrite Eq. (1) as follows:…”

Section: Electron-electron Thermal Bremsstrahlungmentioning

confidence: 99%

“…The boundary values of T 1 , μ 1 , μ 2 and θ max are given in Appendix of Stepney & Guilbert (1983). Here it should be also noted that our definition of G(x, τ) in Eq.…”

Section: Electron-electron Thermal Bremsstrahlungmentioning

confidence: 99%

“…In this section, we present analytic fitting formulae for the electron-electron thermal bremsstrahlung emissivity. Stepney & Guilbert (1983) presented analytic fitting formulae for the temperature range 50 keV ≤ k B T ≤ 1 MeV, which have an overall accuracy that is higher than 5% compared with the numerical integration of Eq. (7).…”

Section: Analytic Fitting Formulaementioning

confidence: 99%

“…In active galactic nuclei, gamma-ray bursters and compact binary sources, the electron energies may be greater than 100 keV. Stepney & Guilbert (1983) studied several important processes contributing to the hightemperature thermal plasmas. Among other processes, they presented analytic fitting formulae for the electron-electron thermal bremsstrahlung emissivity in the temperature range 50 keV ≤ k B T ≤ 1 MeV.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Analytic fitting formulae for relativistic electron-electron thermal bremsstrahlung

Nozawa¹,

Takahashi²,

Kohyama³

et al. 2009

A&A

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We present accurate analytic fitting formulae for electron-electron thermal bremsstrahlung emissivity. The fitting formulae have an overall accuracy of higher than 0.5% for a wide electron temperature range 1 keV ≤ k B T ≤ 7 MeV, which will be useful when analyzing the precision observational data from the non-relativistic regime to mildly-relativistic regime. Assuming the thermal plasma, the present formulae will be also applicable to the relativistic regime.

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Global oscillations of a fluid torus as a modulation mechanism for black‐hole high‐frequency QPOs

Bursa

2005

Astron Nachr

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Abstract. We study strong-gravity effects on modulation of radiation emerging from accreting compact objects as a possible mechanism for flux modulation in QPOs. We construct a toy model of an oscillating torus in the slender approximation assuming thermal bremsstrahlung for the intrinsic emissivity of the medium and we compute observed (predicted) radiation signal including contribution of indirect (higher-order) images and caustics in the Schwarzschild spacetime. We show that the simplest oscillation mode in an accretion flow, axisymmetric up-and-down motion at the meridional epicyclic frequency, may be directly observable when it occurs in the inner parts of accretion flow around black holes. Together with the second oscillation mode, an in-and-out motion at the radial epicyclic frequency, it may then be responsible for the high-frequency modulations of the X-ray flux observed at two distinct frequencies (twin HF-QPOs) in micro-quasars.

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Numerical fits to important rates in high temperature astrophysical plasmas

Cited by 175 publications

References 1 publication

Unstable mass-outflows in geometrically thick accretion flows around black holes

Unstable mass-outflows in geometrically thick accretion flows around black holes

Analytic fitting formulae for relativistic electron-electron thermal bremsstrahlung

Global oscillations of a fluid torus as a modulation mechanism for black‐hole high‐frequency QPOs

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