Physical cause of the NIR flux saturation during bright flares

Investigate the physical mechanism responsible for the saturation (plateau) of near-infrared flux observed during bright flares of Sgr A*, including the April 5 and April 7, 2024 epochs, and determine why the NIR flux ceases to increase while the contemporaneous X-ray flux continues to rise.

Background

Simultaneous JWST and NuSTAR monitoring on April 5, 2024 revealed a strong X-ray flare coincident with a bright NIR flare. The NIR emission plateaued between 10.4 and 10.6 UT while the X-ray flux continued to rise, and similar behavior was noted in the April 7, 2024 data.

Understanding the cause of this NIR saturation is necessary to refine models of particle acceleration, radiative cooling, and beaming in the inner accretion flow, and to reconcile multiwavelength correlations or departures between NIR and X-ray flare profiles.

References

It is not clear why IR flux saturates as this behavior is also seen on our April 7, 2024 epoch observations.

— Simultaneous JWST, NuSTAR, and VLA Monitoring of Sgr A*: A Unified Picture of the Variable IR, X-ray and Radio Emission  (2512.20786 - Yusef-Zadeh et al., 23 Dec 2025) in Section 4.1 (NIR vs X-ray light curves)