Testing alternative theories of gravity by fitting the hot-spot data of Sgr A*

TL;DR

This study tests various alternative gravity theories by fitting hot-spot orbital data around Sgr A* to constrain parameters of modified black hole spacetimes using recent flare observations.

Contribution

It introduces a method to compare different modified black hole models with observational hot-spot data to test gravity theories.

Findings

Orbital frequencies fit observed flare data.

Constraints on parameters of alternative black hole models.

Discrimination between different gravity theories.

Abstract

We are fitting dynamics of electrically neutral hot-spot orbiting around Sgr A* source in Galactic center, represented by various modifications of the standard Kerr black hole (BH), to the three flares observed by the GRAVITY instrument on May 27, July 22, July 28, 2018. We consider stationary, axisymmetric and asymptotically flat spacetimes describing charged BHs in general relativity (GR) combined with non-linear electrodynamics, or reflecting influence of dark matter (DM), or in so called parameterized dirty Kerr spacetimes. We distinguish the spacetimes having different orbital frequencies from the standard Kerr BH, and test various BH spacetimes using the hot-spot data. We show that the orbital frequencies and positions of the hot-spots orbiting the considered BHs, fit the observed positions and periods of the flare orbits and give relevant constrains on the parameters of the considered BH spacetimes and the gravity or other theories behind such modified spacetimes.