Stellar Multiplicity Statistics in APOGEE

Abstract: Nearly every area of astrophysics is impacted by our knowledge of stellar multiplicity, though perhaps none more so than the lifecycles of the stars within close binaries. I seek to characterize these effects through statistical analyses of stellar parameters and sparsely-sampled radial velocity curves determined from the high-resolution spectra of the second Apache Point Observatory Galactic Evolution Experiment (APOGEE-2). I will describe observed trends across a variety of stellar parameters before focusing on my discovery of the complex anti-correlations between the close binary fraction and Fe, O, Mg, and Si abundances. These trends with stellar chemistry reveal the imprints of star formation physics, and I expose further insights into low-mass binary formation by comparing the trends amongst G, K, and M dwarfs. Finally, I demonstrate that rapid stellar rotation is overwhelmingly associated with close binaries; the trends are well-explained by predictions borne from simple theoretical assumptions; and that rotation in close binaries diverges significantly from the predictions of gyrochronolgy.