Why Sagittarius A* flares are so difficult to model?

ABSTRACT:

The center of our galaxy hosts a supermassive black hole (SMBH) of 4.3 millions solar masses called Sagittarius A* (Sgr A*). Its mass and proximity are making the galactic center the ideal laboratory to study general relativity (GR) from parsec scale to few gravitational radii. Orbits of close stars, the S-Stars, allowed recently to detect the gravitational Doppler effect and Swcharzschild precession around a SMBH.

To test GR in the strongest regime, we need to go even closer to the SMBH, by studying the bright and short outbursts of radiation from Sgr A* called flares. Indeed, in 2018, the GRAVITY Collaboration reported the detection of orbital motion of flares around the black hole. These flares have been observed since 2003 from radio to X-ray with puzzling properties.

Numerous models have been developed to explain Sgr A* without reaching a clear consensus. In the last few years, magnetic reconnection appears as the most promising scenario to explain the flares of Sgr A*. However, properly model Sgr A* flares is a very difficult task. In this talk, I will present all the challenges that arise from modelling Sgr A* flares and how can they be used to study GR.