A Nonthermal Bomb Explains the Near-infrared Superflare of Sgr A&z.ast

Abstract

The Galactic center supermassive black hole, Sgr A, has experienced a strong, unprecedented flare in 2019 May when its near-infrared luminosity reached much brighter levels than ever measured. We argue that an explosive event of particle acceleration to nonthermal energies in the innermost parts of the accretion flow- A nonthermal bomb-explains the near-infrared light curve. We discuss potential mechanisms that could explain this event such as magnetic reconnection and relativistic turbulence acceleration. Multiwavelength monitoring of such superflares in radio, infrared, and X-rays should allow a concrete test of the nonthermal bomb model and put better constraints on the mechanism that triggered the bomb.