Parameter study for hot spot trajectories around Sgr$A*$

TL;DR

This paper investigates hot spot trajectories near SgrA* using a general relativistic radiative transfer model, exploring various configurations to match observed flaring behaviors and analyzing black hole spin effects.

Contribution

It introduces a comprehensive parameter study of hot spot motions around SgrA* with a new radiative transfer code, comparing different orbital models to observations.

Findings

Super-Keplerian frequencies favor certain hot spot models.

Conical trajectories fit lower orbital frequencies better.

Black hole spin and viewing angle are hard to distinguish observationally.

Abstract

Intense flaring events in the near-infrared and X-ray wavebands of our Galactic Center have been the subject of research for decades. In recent years, the GRAVITY instrument of the Very Large Telescope captured the motion and polarimetric signature of such a flare in close proximity to the supermassive black hole. This study aims to investigate a broad parameter space for hot spot motion in the vicinity of Sgr$A*$ and reproduce the observed flaring behavior. To this end, we have developed a General Relativistic Radiative Transfer code and conducted a parameter study including both planar and ejected hot spot configurations around supermassive black holes. Super-Keplerian orbital frequencies are favored by circular equatorial, cylindrical and parabolic models, whereas conical hot spot trajectories provide a better fit for orbital frequencies below the Keplerian value. Additionally, a distant observer cannot effectively differentiate between Schwarzschild and Kerr black holes, as well as face-on orbits at different observation angles.