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Abstract The time-variable emission from the accretion flow of Sgr A*, the supermassive black hole at the Galactic center, has long been examined in the radio-to-millimeter, near-infrared (NIR), and X-ray regimes of the electromagnetic spectrum. However, until now, sensitivity and angular resolution have been insufficient in the crucial mid-infrared (MIR) regime. The MIRI instrument on JWST has changed that, and we report the first MIR detection of Sgr A*. The detection was during a flare that lasted about 40 minutes, a duration similar to NIR and X-ray flares, and the source's spectral index steepened as the flare ended. The steepening suggests that synchrotron cooling is an important process for Sgr A*'s variability and implies magnetic fields strengths ~ 40–70 G in the emission zone. Observations at 1.3 mm with the Submillimeter Array revealed a counterpart flare lagging the MIR flare by ≈10 minutes. The observations can be self-consistently explained as synchrotron radiation from a single population of gradually cooling high-energy electrons accelerated through (a combination of) magnetic reconnection and/or magnetized turbulence. 

Optical coatings play a vital role in sensing technologies. The development of new coatings that exhibit minimal optical losses requires a detailed understanding of the development of defects within them. Current methods of defect characterization involve direct microscope imaging or x-ray diffraction studies in the case of crystallites. In this paper, we demonstrate the characterization of coating defects using light scattering, which can yield information about their size, location, and index of refraction. The method requires measuring the scattered power of each individual defect as a function of angle and comparing the data with theoretical models. Finally, we argue that this method can be used for the determination of the defect location within a multi-layer stack.