Intrinsic Electron Injection Profile of Sgr A* Flares

Determine the intrinsic temporal injection profile of the non-thermal electron population responsible for the mid-infrared flare emission from Sagittarius A* within the compact, orbiting emission region near the event horizon, given that the observed flare shape can be fit with a Gaussian injection profile modified by Doppler boosting due to orbital motion but the true injection profile is unknown.

Background

The paper presents the first mid-infrared detection of a flare from Sagittarius A* using JWST/MIRI, observing a 40–50 minute event with spectral index steepening consistent with synchrotron cooling in magnetic fields of roughly 40–70 G. To interpret the observed light curves, the authors develop a simple one-zone synchrotron model in which electrons are injected with a time-dependent rate into a compact emission region with constant magnetic field and orbital motion, including Doppler boosting and gravitational redshift.

Within this modeling framework, the flare shape is successfully reproduced by assuming a Gaussian electron injection profile combined with Doppler effects from orbital motion. However, the authors explicitly note that the intrinsic electron injection profile is unknown. Resolving the true temporal form of electron injection is central to identifying the underlying acceleration mechanism (e.g., reconnection or turbulence), constraining the duration of acceleration, and refining predictions for multi-wavelength counterparts.