Author ORCID Identifier
Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
Binary stellar systems consisting of at least two stars with separations >10,000 au are essential tools in astronomy. However, we still do not fully understand how these systems formed as their separations are larger than that of a typical protostellar core. Furthermore, a majority of these systems are thought to be higher order multiples, i.e., triples, quadruples, etc., although no definitive fraction has been published to date. Determining what fraction of these systems are higher order multiples and examining the properties of those systems will set constraints that will help determine the origin of these extremely wide systems. To this end, we constructed the SUPERWIDE catalog of wide binaries using Gaia DR2 astrometry. Our search method consists of a two part Bayesian analysis which identifies physical pairs based on their angular separations, proper motion difference, and distance differences between the stars in the pair. This analysis resulted in a catalog of 99,203 pairs having probabilities greater than 95% of being gravitationally bound systems. We show that the predictable behavior of K-dwarfs in the H-R diagram makes it possible to devise a simple method to identify additional unresolved components using readily available magnitudes, colors, and parallaxes. By comparing the over-luminosities of the components to each other, we were able to identify over-luminous components and most likely host unresolved companions. Examining this, we determine a lower limit on the higher order multiplicity fraction of K+K wide binaries to be 40.3%. We notice a slight dependence on the higher order multiplicity with metallicity and no dependence with physical separation. Finally, we report the results of several speckle campaigns on the widest halo and low-mass disk binaries and find relatively few companions. As it is expected that the majority of these systems should have a third component, we believe this points to substantial dynamical interactions occurring in these systems and the companions are below the separation limit we can examine with speckle imaging. However, even with the lack of companions detected, we have put limits on where potential companions can reside in these systems.
Hartman, Zachary, "Examining the Higher-Order Multiplicity of Low-mass Wide Binary Systems." Dissertation, Georgia State University, 2021.
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