ASTRONOMY COLLOQUIUM

M dwarfs are the most common type of star in the galaxy, and they abound with small planets on close-in orbits that can be studied with the transit and radial velocity techniques. I will present the results of overlapping projects that examine the frequencies, bulk compositions, and atmospheres of these compelling planets. The first project is a volume-limited survey of transiting planets discovered by TESS. By modeling the completeness of TESS, we have placed new constraints on the frequencies of planets orbiting the latest M dwarfs. Additionally, using my group's new MAROON-X spectrograph, we have measured precise masses of the TESS volume-limited sample, revealing the demographics of their bulk compositions. Finally, we are searching for atmospheres on M dwarf terrestrial planets using JWST thermal emission measurements. So far, we have placed tight limits on the presence of secondary atmospheres for a number of planets. These results have ramifications for hypotheses about atmospheric retention in the face of loss processes (i.e., the "Cosmic Shoreline") and the formation of silicate vapor atmospheres from the evaporation of solid surfaces.