Constraints on Post-Superflare Exo-Auroral Emission with SOAR and the Evryscope Fast Transient Engine

High-energy particles from M-dwarf superflares--flares with energy \(\geq 10^{33}\) erg--can dramatically impact habitable-zone planets around these cool stars, with possible effects including the excitation of intense aurorae as particles interact with planetary atmospheres. Prior work has demonstrated that Earthlike atmospheres can produce excess emission in M-dwarf spectra, with the star/planet contrast ratio increasing by orders of magnitude in the green 5577-Å auroral line to levels potentially detectable by future surveys. The Evryscopes are gigapixel-scale telescope arrays at Mount Laguna Observatory and Cerro-Tololo Inter-American Observatory; coupled with the Evryscope Fast Transient Engine (EFTE), which scans Evryscope images in real time for transient phenomena, the systems have the unprecedented ability to identify superflares across the entire sky as they begin, enabling rapid spectroscopic follow-up. With the Evryscopes' all-sky coverage, far more--and far brighter--flares are observable than in surveys that focus on individual targets. Using the Goodman spectrograph on the 4.1-m SOAR telescope, we follow the spectroscopic evolution of M-dwarf superflares as they happen. Preliminary results include the strongest-yet upper limits to be placed on auroral emission in the atmospheres of Earthlike planets orbiting M-dwarf stars.