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Numerical, two-dimensional, time-dependent hydrodynamical models of geometrically thick accretion discs around black holes are presented. Accretion flows with non-effective radiation cooling (ADAFs) can be both convectively stable or…

Astrophysics · Physics 2009-09-25 Igor V. Igumenshchev

We describe hot, optically-thin solutions for one-temperature accretion disks around black holes. We include cooling by synchrotron, bremsstrahlung, and Comptonization. Our solutions are thermally and viscously stable, with gas temperatures…

Astrophysics · Physics 2016-08-30 A. A. Esin , R. Narayan , E. Ostriker , I. Yi

In a previous paper we have written down equations describing steady-state, optically thin, advection-dominated accretion onto a Kerr black hole (Gammie and Popham 1997, hereafter Paper I). In this paper we survey the numerical solutions to…

Astrophysics · Physics 2009-10-30 Robert Popham , Charles F. Gammie

Based on no-outflow assumption, we investigate steady state, axisymmetric, optically thin accretion flows in spherical coordinates. By comparing the vertically integrated advective cooling rate with the viscous heating rate, we find that…

High Energy Astrophysical Phenomena · Physics 2015-06-23 Wei-Min Gu

The effectiveness of the thermal coupling of ions and electrons in the context of optically thin, hot accretion flows is investigated. In the limit of complete coupling, we focus on the one-temperature accretion flows. Based on a global…

Astrophysics · Physics 2009-11-13 Feng Yuan , Ronald E. Taam , Yongquan Xue , Wei Cui

A model for axisymmetric magnetized accretion flow is proposed. The dominant mechanism of energy dissipation is assumed to be the magnetic diffusivity due to turbulence in the accretion flow. In analogy to the advection-dominated accretion…

Astrophysics · Physics 2009-11-07 Mohsen Shadmehri

Advection-dominated accretion flows (ADAFs) are known to be convectively unstable for low values of the viscosity parameter alpha. Two-dimensional axisymmetric hydrodynamic simulations of such flows reveal a radial density profile which is…

Astrophysics · Physics 2009-10-31 Igor V. Igumenshchev , Marek A. Abramowicz , Ramesh Narayan

We calculate the radiation spectra from advection-dominated accretion flows (ADAFs), taking into account the effects of a global magnetic field. Calculation is based on the analytic model for magnetized ADAFs proposed by Kaburaki, where a…

Astrophysics · Physics 2009-10-31 Motoki Kino , Osamu Kaburaki , Naohiro Yamazaki

Recent numerical simulations of radiatively inefficient accretion flows onto compact objects have shown that convection is a general feature in such flows. Dissipation of rotational and gravitational energies in the accretion flows results…

Astrophysics · Physics 2009-11-06 Igor V. Igumenshchev , Marek A. Abramowicz

We investigate the transition of a radiatively inefficient phase of a viscous two temperature accreting flow to a cooling dominated phase and vice versa around black holes. Based on a global sub-Keplerian accretion disc model in steady…

High Energy Astrophysical Phenomena · Physics 2014-11-20 Monika Sinha , S. R. Rajesh , Banibrata Mukhopadhyay

We consider height-integrated equations of an advection-dominated accretion flow (ADAF), assuming that there is no mass outflow. We include convection through a mixing length formalism. We seek self-similar solutions in which the rotational…

Astrophysics · Physics 2009-10-31 Ramesh Narayan , Igor V. Igumenshchev , Marek A. Abramowicz

In order to study the outflows from accretion disks, we solve the set of hydrodynamic equations for accretion disks in the spherical coordinates ($r\theta\phi$) to obtain the explicit structure along the $\theta$ direction. Using…

High Energy Astrophysical Phenomena · Physics 2011-05-25 Cheng-Liang Jiao , Xue-Bing Wu

Observations and numerical magnetohydrodynamic (MHD) simulations indicate the existence of outflows and ordered large-scale magnetic fields in the inner region of hot accretion flows. In this paper we present the self-similar solutions for…

Astrophysics · Physics 2009-11-13 De-Fu Bu , Feng Yuan , Fu-Guo Xie

In this paper, the self-similar solution of resistive advection dominated accretion flows (ADAF) in the presence of a pure azimuthal magnetic field is investigated. The mechanism of energy dissipation is assumed to be the viscosity and the…

High Energy Astrophysical Phenomena · Physics 2015-06-03 Kazem Faghei

We study the formation of the spectra in advection dominated accretion flows (ADAFs) around Kerr black holes. We use a Monte Carlo approach and fully general relativistic treatment to follow the paths of individual photons and model their…

Astrophysics · Physics 2007-05-23 A. Kurpiewski , M. Jaroszynski

This article reviews the physics of advection-dominated accretion flows (ADAFs) and describes applications to several black hole X-ray binaries and galactic nuclei. The possibility of using ADAFs to explore the event horizons of black holes…

Astrophysics · Physics 2007-05-23 Ramesh Narayan , Rohan Mahadevan , Eliot Quataert

It has been suggested that the laws of thermodynamics are violated by what we have called a convection-dominated accretion flow (or a 1/2-law accretion flow) -- an accretion flow characterized by a constant outflow of energy. We show that…

Astrophysics · Physics 2007-05-23 Andrei Gruzinov

We investigated effects on flow variables of transonic advection-dominated accretion flows (ADAFs) for different outer boundary locations (BLs) with a changing energy constant ($E$) of the flow. We used the ADAF solutions and investigated a…

High Energy Astrophysical Phenomena · Physics 2019-05-15 Rajiv Kumar , Wei-Min Gu

Two-dimensional (axially symmetric) numerical hydrodynamical calculations of accretion flows which cannot cool through emission of radiation are presented. The calculations begin from an equilibrium configuration consisting of a thick torus…

Astrophysics · Physics 2009-10-31 James M. Stone , James E. Pringle , Mitchell C. Begelman

We solve the radiation-hydrodynamic (RHD) equations of supercritical accretion flows in the presence of radiation force and outflow by using self similar solutions. Compare with the pioneer works, in this paper we consider power-law…

High Energy Astrophysical Phenomena · Physics 2016-06-01 Fatemeh Zahra Zeraatgari , Shahram Abbassi , Amin Mosallanezhad