Synchrotron X-ray flares in Sgr A* powered by relativistic collisionless magnetic reconnection: a kinetic view

Relativistic magnetic reconnection is an appealing candidate for driving nonthermal particle acceleration that can power intense high-energy flares in many compact astrophysical sources, including accreting black holes. First-principles, fully kinetic numerical simulations of collisionless relativistic reconnection in recent years have given us a detailed and rigorous physical picture of this process. This quantitative picture includes the dependence of the key relativistic particle acceleration characteristics, such as power-law indices and high-energy cutoffs, on the main governing system parameters, e.g., the ambient plasma magnetization, system size, and radiative cooling strength. In this presentation, I will make use of this kinetic information, in combination with the observational energetics and flare-duration constraints, to construct a basic model demonstrating the plausibility of the relativistic reconnection-powered synchrotron scenario for the simultaneous near-infrared and X-ray flares observed from the black hole Sgr A* at our Galactic Center. I will also discuss the general observational properties of reconnection-powered synchrotron flares, with applications to broad classes of astrophysical sources.

Work supported by NASA ATP grants 80NSSC20K0545 and 80NSSC22K0828 and NSF grants AST-1806084 and AST-1903335.