Light and shadow in the Galactic Center - On the detection of the relativistic periastron shift of star S2 in the Galactic Center

TL;DR

This paper investigates the relativistic effects in the orbit of star S2 around the supermassive black hole SgrA* in the Galactic Center, including the detection of the relativistic periastron shift and implications for black hole properties.

Contribution

The study provides a detailed analysis of the relativistic periastron shift of star S2 and discusses methods to probe stronger relativistic effects near SgrA* using plasma emissions and lightcurve modeling.

Findings

Detection of relativistic periastron shift of star S2

Estimation of the relativistic parameter ${} = r_s/r_p$ for S2

Discussion of shadow effects due to light bending near SgrA*

Abstract

We report on the nature of prominent sources of light and shadow in the Galactic Center. With respect to the Bremsstrahlung X-ray emission of the hot plasma in that region the Galactic Center casts a 'shadow'. The 'shadow' is caused by the Circum Nuclear Disk that surrounds SgrA* at a distance of about 1 to 2 parsec. This detection allows us to do a detailed investigation of the physical properties of the surroundings of the super massive black hole. Further in, the cluster of high velocity stars orbiting the central super massive black hole SgrA* represents an ideal probe for the gravitational potential and the degree of relativity that one can attribute to this area. Recently, three of the closest stars (S2, S38, and S55/S0-102) have been used to conduct these investigations. In addition to the black hole mass and distance a relativistic parameter defined as ${\Upsilon}=r_s/r_p$ could be derived for star S2. The quantity $r_s$ is the Schwarzschild radius and $r_p$ is the pericenter distance of the orbiting star. Here, in this publication, we highlight the robustness and significance of this result. If one aims at investigating stronger relativistic effects one needs to get closer to SgrA*. Here, one can use the emission of plasma blobs that orbit SgrA*. This information can be obtained by modeling lightcurves of bright X-ray flares. Finally, we comment on the shadow of the SgrA* black hole expected due to light bending and boosting in its vicinity.