Double Compton and cyclo-synchrotron in super-Eddington discs, magnetized coronae and jets

作者：McKinney Jonathan C^*; Chluba Jens; Wielgus Maciek; Narayan Ramesh; Sadowski Aleksander

来源：Monthly Notices of the Royal Astronomical Society, 2017, 467(2): 2241-2265.

DOI：10.1093/mnras/stx227

• accretion, accretion discs
• black hole physics
• MHD
• radiation: dynamics
• galaxies: jets
• X-rays: binaries

Black hole accretion discs accreting near the Eddington rate are dominated by bremsstrahlung cooling, but above the Eddington rate, the double Compton process can dominate in radiationdominated regions, while the cyclo-synchrotron can dominate in strongly magnetized regions like a corona or a jet. We present an extension to the general relativistic radiationmagnetohydrodynamic 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. The HARMRAD code and associated analysis and visualization codes have been made open-source and are publicly available at the github repository website. 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 discs accreting at Eddington to super-Eddington rates. We find that double Compton dominates bremsstrahlung in the disc within a radius of r similar to 15r(g) (gravitational radii) at 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 similar to 10(9)K is similar to 100 times higher than the disc's blackbody temperature. Our results show the importance of double Compton and synchrotron in super-Eddington discs, magnetized coronae and jets.

• 出版日期2017-5
• 单位MIT