A Study of Stellar Spins in Open Clusters

Stars in open clusters offer unique insight into the outcomes of star formation through their assumed coeval formation. These stars’ shared age, metallicity, and formation environment make each cluster a benchmark in temporal, chemical, and dynamical evolution. Among the quantities that offer a glimpse into a cluster’s past is the projected inclination, or the projected angle between a star’s rotation axis and the observer’s line of sight. In this dissertation containing three journal articles, I analyze spectroscopic and photometric data to determine the projected inclinations of stars in 15 open clusters, placing constraints on the spin-axis distributions of twelve. I find that nine out of twelve constrained clusters (75%) have spin-axis orientations consistent with isotropy, and I establish a lower limit of four out of twelve (33%) isotropic clusters at 70% confidence, assuming no correlation of spins between clusters. I also identify three clusters whose spin-axis distributions can be better described by an aligned fraction of stars combined with an isotropic distribution. The stars modeled as aligned in these three clusters may have inherited their spins from shared substructure within their star-forming clump, or their inclination values may be influenced by systematic error. Overall, no cluster displays an unambiguous signature of spin alignment, and 96% of the stars in the sample are consistent with isotropic orientations in their respective clusters. The results of my dissertation offer support for the dominance of turbulence over ordered rotation in clumps and do not suggest alignment of rotation axes and magnetic fields in protostars. Future work will benefit from the reduction of systematic errors via multi-object spectrograph observing campaigns, increased understanding of stellar radius inflation, and a new space telescope enabling further spectro-photometric as well as asteroseismic studies