Dr F. Hossein-Nouri (CTP PAS PAS): Gas-rich environment effect on low-frequency gravitational waves
Channel: Centrum Fizyki Teoretycznej PAN
Date: 13/12/2023

Dr Fatemeh Hossein-Nouri (Center for Theoretical Physics PAS).
Gas-rich environment effect on low-frequency gravitational waves from supermassive black hole binaries.

The Laser Interferometer Space Antenna (LISA) is the third large mission of ESA's Cosmic Vision program. It is scheduled for launch in the mid-2030s. LISA will be sensitive to low-frequency (mHz) gravitational waves (GW) emitting from different astrophysical sources including inspiring and merging supermassive black holes. Such binary systems are usually embedded in an accretion disk environment at the center of the active galactic nuclei (AGN). Studies suggest the gas environment leaves measurable imprints on the GW signal for Extreme Mass Ratio Inspiral (EMRI) binary black hole cases. This effect appears as a phase shift in the GW signal demonstrating the delay or acceleration of the merger. The effect of the gaseous environment on the GW signal is strongly dependent on the disk's parameters, therefore it is believed that future LISA detections will provide us with precious information about the physics of AGN accretion disks. In this talk, I present the recent study in our group investigating this effect by measuring the disk torques on a hypothetical low-mass orbiting object by modelling several magnetized tori. In our numerical simulations, we study the angular momentum transport and turbulence generated by the magnetorotational instability (MRI). We quantify the disk's effective alpha-viscosity and its evolution over time. We apply our numerical results to estimate the relativistic viscous torque and the GW phase shift due to this MRI-driven turbulence.
‍Wednesday colloquium at CTP PAS – 2023-12-06