The non-negligible activity of inactive M dwarfs measured by TESS and implications for JWST Observations

Stellar flares on planet-hosting stars exert both short and long-term influences on their planets. Particularly impactful on planetary atmospheres, these flares can induce atmospheric erosion while also acting as drivers for disequilibrium physical and chemical processes. The increasing volume and precision of infrared observations facilitated by JWST presents an opportunity to deepen our understanding of the impact these phenomena have on planets. Planet-hosting M dwarfs are very appealing targets for transmission spectroscopy observations due to the larger transit depths associated with higher S/N detections. However, M dwarfs are typically highly active stars, which means quantifying the activity of these stars can be crucial for interpreting results of any searches for planet atmospheres. In this talk, I focus on the M dwarfs GJ 1132 and LHS 1140, which are planet-hosting targets exhibiting low activity, and are scheduled for follow-up JWST observations later this year. We searched the available TESS light curves of these stars for flares, and compare their flare frequency distributions with those of known active and inactive M dwarfs. I will also discuss implications of these stellar activity measurements for interpreting future JWST spectra of these planets’ atmospheres.