Quasi-periodic oscillations from relativistic hydrodynamical slender tori

TL;DR

This study uses relativistic hydrodynamical simulations to investigate quasi-periodic oscillations in a torus around a Schwarzschild black hole, identifying how different velocity perturbations excite specific oscillation modes.

Contribution

It demonstrates the excitation of specific oscillation modes in a relativistic hydrodynamical torus through targeted velocity perturbations, using advanced simulation and ray-tracing techniques.

Findings

Horizontal perturbation excites radial and plus modes.

Vertical perturbation excites vertical and X modes.

Diagonal perturbation excites a combination of radial and vertical modes.

Abstract

We simulate an oscillating purely hydrodynamical torus with constant specific angular mo- mentum around a Schwarzschild black hole. The goal is to search for quasi-periodic oscil- lations (QPOs) in the light curve of the torus. The initial torus setup is subjected to radial, vertical and diagonal (combination of radial and vertical) velocity perturbations. The hydro- dynamical simulations are performed using the general relativistic magnetohydrodynamics code Cosmos++ and ray-traced using the GYOTO code. We found that a horizontal velocity perturbation triggers the radial and plus modes, while a vertical velocity perturbation trig- gers the vertical and X modes. The diagonal perturbation gives a combination of the modes triggered in the radial and vertical perturbations.