GRMHD Simulations of Magnetized Accretion Disk/Jet: Variabilities of Black Holes and Spectral Energy Distributions in Magnetic States

Abstract

We perform three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations of a near-maximally spinning black hole (spin parameter, a = 0.998) with varying initial magnetic field geometries, systematically exploring the parameter space connecting magnetically arrested disk (MAD), intermediate (INT), and standard and normal evolution (SANE) accretion states. The magnetic flux threading the black hole horizon emerges as the fundamental state variable controlling jet efficiency, flow magnetization, and radiative output across all three states. We introduce complementary diagnostics-broadband spectral energy distributions spanning radio through hard X-ray frequencies and time-resolved X-ray light curves-that together connect simulation dynamics directly to multiwavelength observables. The radiative output follows a clear MAD > INT > SANE hierarchy in time-averaged luminosity, mean X-ray emission, as well as variability. Furthermore, MAD exhibits the highest fractional variability through quasi-periodic magnetic flux eruption events, and INT and SANE show moderate variability driven by episodic reconnection and stochastic MRI turbulence, respectively. Scaling to GRS 1915+105, Cyg X-1, and HLX-1, we demonstrate that all twelve temporal classes of GRS 1915+105 map naturally onto our three magnetic states, Cyg X-1's persistent hard state is reproduced by a sustained INT configuration, and HLX-1's extreme luminosities arise through efficient Blandford-Znajek extraction in MAD states scaled to higher black hole mass.

Published in Universe as an invited article to the Special Issue "Magnetized Dense Matter in Compact Stars: From Fundamental Properties to Astrophysical Observables", 30 pages, 8 Figures, 2 Tables

References in corpus (11)

• X-ray Properties of Black-Hole Binaries
• Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds
• A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass
• Flux eruption events drive angular momentum transport in magnetically arrested accretion flows
• Two years of INTEGRAL monitoring of GRS 1915+105 Part 1: multiwavelength coverage with INTEGRAL, RXTE, and the Ryle radio Telescope
• A new lepto-hadronic model applied to the first simultaneous multiwavelength data set for Cygnus X--1
• Rapid Black Hole Spin-down by Thick Magnetically Arrested Disks
• Accretion Flow Morphology in Numerical Simulations of Black Holes from the ngEHT Model Library: The Impact of Radiation Physics
• Misaligned magnetized accretion flows onto spinning black holes: Magneto-spin alignment, outflow power, and intermittent jets
• On the Universality of Energy Extraction from Black Hole Spacetimes
• GRMHD simulations of black hole accretion variabilities: Implications to hard state X-ray binary transients