Seminars

"Gravitational wave emission from turbulent accretion disks around black holes"

Samik Mitra (Astrophysics and Relativity Group International Centre for Theoretical Sciences, Bengaluru, India)

Magneto-rotational instability (MRI) is the primary mechanism for driving turbulence in accretion disks. Such instability disrupts the axial symmetry of the system and can stochastically excite the quasi-normal ringing of the black holes (BHs), which could emit gravitational waves (GWs). Motivated with this, we investigate stochastic GW signals from turbulent, magnetized accretion disks around spinning BHs. In doing so, we conduct three global general relativistic magnetohydrodynamic (GRMHD) simulations of (i) standard and normal evolution (SANE), (ii) sub-SANE, and (iii) magnetically arrested disk (MAD) models. The results from these simulations are used as a source in the Teukolsky equation to compute the emitted GW energy. We compare the GW signals from these models and identify what aspects of the gas physics, including turbulence and magnetic fields, effectively excite BH quasi-normal modes (QNMs). We assess whether the stochastic GW backgrounds (SGWBs) generated in each scenario approach the sensitivity curves of future gravitational wave detectors, offering new insights into multimessenger astrophysics and accretion physics.