General relativistic numerical simulation of sub-Keplerian transonic accretion flows on to rotating black holes: Kerr space–time

Abstract

We study time evolution of sub-Keplerian transonic accretion flows onto black holes using a general relativistic numerical simulation code. We perform simulations around the black holes having non-zero rotation. We first compare one-dimensional simulation results with theoretical results and validate the performance of our code. Next, we present results of axisymmetric, two-dimensional simulation of advective flows. In the literature, there is no solution which describes steady shock solutions in two dimensions. However, our simulations produce these centrifugal force supported steady shock waves even in presence of strong dragging of inertial frames. Since the post-shock region could be hot and upscatter photons through Comptonization, these shock would put imprints on the spectra. Thus, our solutions, which represent truly new results, could be useful to measure spins through radiation spectrum of accreting Kerr black holes.

Evidence of Outflow-induced Soft Lags of Galactic Black Holes

“…Numerical simulations of this advective component shows presence of strong winds Molteni et al (1994) from the Compton cloud or CENtrifugal pressure supported BOundary Layer also known as CENBOL. Extending this to full general relativistic flow, recently Kim et al (2019) showed that most of the outflow has sub-escape velocity and returns back to the equatorial region while only a fraction can achieve escape velocity and leave the system along the axis from Compton cloud. We conjecture that this return flow down-scatters hard photons and creates soft photons with large time lag.…”

Effects of resistivity on standing shocks in low angular momentum flows around black holes

“…All the above-mentioned simulation works addressed the accretion flow behavior around a non-rotating black hole by relying on pseudo-Newtonian potential. Recently, general relativistic highresolution shock-capturing simulation code was used to study the scenario in Schwarzschild (Kim et al 2017) and Kerr (Kim et al 2019) space-time which further established the formation of a standing shock in hydrodynamic (HD) flow around a non-rotating as well as rotating black hole in full general relativistic treatment. However, till now there has been only one work taking into account different magnitudes of magnetic field strength in such flows in the presence of standing shocks (Okuda et al 2019).…”

Low angular momentum relativistic hot accretion flow around Kerr black holes with variable adiabatic index

“…Meanwhile, the study of the shock waves in the accretion flow around black holes is being carried out by the numerous group of workers both theoretically as well as numerically (Fukue 1987;Chakrabarti 1989;Yang & Kafatos 1995;Molteni et al 1996;Ryu, Chakrabarti, & Molteni 1997;Lu et al 1999;Becker & Kazanas 2001;Fukumura & Tsuruta 2004;Das 2007;Kumar et al 2013;Das et al 2014;Okuda & Das 2015;Suková & Janiuk 2015;Sarkar & Das 2016;Aktar et al 2017;Dihingia, Das, & Mandal 2018). Very recently, Kim et al (2017Kim et al ( , 2018 showed the formation of shocks in the accretion flow around black holes using general relativistic hydrodynamical numerical simulation. In addition, Nishikawa et al (2005) and Fukumura et al (2016) also examined the shock solutions in the GRMHD framework under suitable physical conditions.…”