Near-Infrared and X-ray Quasi-Periodic Oscillations in Numerical Models of Sgr A*

TL;DR

This paper presents numerical models of Sgr A* that reveal transient near-infrared and X-ray quasi-periodic oscillations caused by MHD turbulence, with implications for understanding accretion flow dynamics near the black hole.

Contribution

The study introduces relativistic radiative models showing transient QPOs linked to nonaxisymmetric structures and magnetic filaments, providing new insights into accretion flow variability.

Findings

QPOs are associated with nonaxisymmetric $m=1$ structures.

Power spectra show peaks near the orbital frequency at ISCO.

QPO amplitudes depend on electron distribution functions.

Abstract

We report transient quasi-periodic oscillations (QPOs) on minute timescales in relativistic, radiative models of the galactic center source Sgr A*. The QPOs result from nonaxisymmetric $m=1$ structure in the accretion flow excited by MHD turbulence. Near-infrared (NIR) and X-ray power spectra show significant peaks at frequencies comparable to the orbital frequency at the innermost stable circular orbit (ISCO) $f_o$. The excess power is associated with inward propagating magnetic filaments inside the ISCO. The amplitudes of the QPOs are sensitive to the electron distribution function. We argue that transient QPOs appear at a range of frequencies in the neighborhood of $f_o$ and that the power spectra, averaged over long times, likely show a broad bump near $f_o$ rather than distinct, narrow QPO features.