Double Compton and Cyclo-Synchrotron in Super-Eddington Discs, Magnetized Coronae, and Jets

Abstract

We present an extension to the general relativistic radiation magnetohydrodynamic code HARMRAD to account for emission and absorption by thermal cyclo-synchrotron, double Compton, bremsstrahlung, low-temperature OPAL opacities as well as Thomson and Compton scattering. We approximate the radiation field as a Bose-Einstein distribution and evolve it using the radiation number-energy-momentum conservation equations in order to track photon hardening. We perform various simulations to study how these extensions affect the radiative properties of magnetically-arrested disks accreting at Eddington to super-Eddington rates. We find that double Compton dominates bremsstrahlung in the disk within a radius of r ∼ 15r g (gravitational radii) at a hundred times the Eddington accretion rate, and within smaller radii at lower accretion rates. Double Compton and cyclo-synchrotron regulate radiation and gas temperatures in the corona, while cyclo-synchrotron regulates temperatures in the jet. Interestingly, as the accretion rate drops to Eddington, an optically thin corona develops whose gas temperature of T ∼ 10 9 K is ∼ 100 times higher than the disk's black body temperature. Our results show the importance of double Compton and synchrotron in super-Eddington disks, magnetized coronae, and jets.

Radiative striped wind model for gamma-ray bursts

“…Piran (1999); Mészáros (2006), and more recently Kumar & Zhang (2015); Pe'er (2015)). The acceleration can be provided either by the thermal pressure if magnetic fields are sub-dominant, UB ≪ Uγ (this is the classical "fireball" model; see Paczynski 1986Paczynski , 1990Rees & Meszaros 1992Piran et al 1993), or at the expence of magnetic energy, if UB ≫ Uγ (Spruit et al 2001;Lyutikov 2006;Narayan et al 2007;Tchekhovskoy et al 2008;Komissarov et al 2009;McKinney & Uzdensky 2012). In addition, the high efficiency of GRB prompt phase (Cenko et al 2011) implies that the plasma should be an efficient emitter during and/or after its acceleration.…”

Slim Accretion Disks: Theory and Observational Consequences

“…Ghoreyshi and Shadmehri [79] propose to add the radial viscous force. McKinney et al [80] show that double Compton and cyclo-synchrotron cooling is also important and affects the conclusions about the temperature in the innermost part of a slim disk. Convection is certainly present in the accretion disks [e.g.…”

Gamma-Ray Bursts Generated by Hyper-Accreting Kerr Black Hole

“…Luminous disk accretion onto rotating black holes general governed by magnetohydrodynamic (MHD) equations. This spinning, magnetized black hole with thin asymmetric turbulent relativistic disk widely simulated and MHD equations are numerically solved [25] [30]. Then, traditionally the equations of relativistic MHD are given in the conserved form: the mass continuity equation…”

“…But the physical sources of luminous burst radiation have not yet been well settled. Thus, we are intended to study the evolution of rapidly rotating, accreting BH in full general relativity and the relativistic accretion flow in MHD and its numerical calculation with accurate GRMHD code [30]. We approach the outflow radiation using MHD conserved equations to construct spectrum of radiative heating due to viscous and magnetic dissipation in general relativistic Kerr geometry.…”