SIMBAD references

Flux variability is a fundamental channel of information from Sgr A* because of its direct probe of processes occurring within an accretion disk under strong gravity. We present simultaneous JWST, NuSTAR, and Very Large Array observations of Sgr A* on 2024 April 5. We report the detection of a strong X-ray flare with a duration of about 40 minutes and a luminosity of 5.2 × 10³⁵ erg s^–1 coincident with a bright near-IR (NIR) flare, and a brightening in radio about an hour later. We investigate the candidate physical mechanisms for the X-ray flare emission and conclude that this can best be explained by inverse Compton scattering of NIR flare radiation. We propose a dynamic scenario analogous to a coronal mass ejection in which a magnetic flux rope is ejected from Sgr A*'s inner accretion flow with a current sheet extending down from the rope to the bulk of the accretion flow. The accelerated electrons are continually ejected from the reconnection X-point with a bulk flow at the Alfvén speed of 0.7c. IR radiation from the approaching energetic electrons is enhanced by beaming and upscattered by thermal electrons in the accretion flow to produce the strong X-ray flare. Meanwhile, the relativistic electrons moving in the opposite direction away from the disk experience weaker magnetic fields and so radiate at longer wavelengths. They feed into the magnetic flux tube explaining the detected delayed radio emission. This physical picture attempts to unify the origin of the variable emission from Sgr A* at IR, X-ray, and radio/submillimeter wavelengths.