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Abstract
While thousands of exoplanets have been discovered to date, there are still many open questions with regards to their formation, evolution, and occurrence. These questions are especially difficult to answer for the smallest (and most difficult to observe) planets. As the typical planet signal is inversely proportional to the size of its host star, M dwarfs provide us the best opportunity to study small, Earth-like planets. The radii, masses, and stellar properties of these planetary systems will be necessary in order to understand their compositions, where they formed, their migration history, and even the state of their atmospheres. While photometric surveys such as TESS and Kepler can give us insight into the orbital periods and radii of these planets, follow-up of these systems is necessary in order to measure their masses and orbits. In this dissertation, I highlight several different projects that directly contribute to our understanding of M dwarf planet occurrence, formation, and evolution using the MAROON-X instrument. Firstly, I discuss several different projects in which I used MAROON-X to measure the orbital obliquities of two M dwarf systems (TRAPPIST-1 and LP 267-75) using the Rossiter-McLaughlin effect. Overall, I found that these M dwarfs were aligned with the orbits of their planets, which may imply that small, fully-convective M dwarfs are highly effective at aligning their planets. Later, I describe several projects that utilized MAROON-X’s stability and red wavelength coverage to measure the masses of M dwarf planets. These projects include HUMDRUM (Hunting for M Dwarf Rocky Planets Using MAROON-X), a volume-limited survey I led that measured the masses of nearby M dwarf rocky planets that had transits identified via TESS. Overall, I found that rocky M dwarf planets tend to have Earthlike or slightly sub-Earth densities. However, many of these planets are unlikely to have thick atmospheres, making them difficult to follow-up with atmospheric reconnaissance studies with instruments like JWST.