Program: GS-2019B-Q-213

We propose to observe 53 pairs of Halo wide binary stars (projected separation>1,000 AU) over 3 nights with 'Alpoeke and Zorro on both of the Gemini 8m telescopes with the goal of finding whether these systems consist of two effectively ”single” stars, or if they are in fact hierarchical systems consisting of three or more stars with one or more shorter period, close stellar pair. Halo wide binaries have not been studied due to both their distances and lack of identified systems. The release of large catalogs has made the latter much easier to correct. The Halo wide binary systems selected for this study were identified through a Bayesian analysis of the high proper motion stars in Gaia DR2 (> 40 mas/yr). These observations will allow us to examine the higher order multiplicity fraction of halo wide binaries and see if there are any differences between that fraction and the one being found in the Disk. If differences are found, it may indicate that Halo wide binaries formed differently than their wide counterparts in the Disk of the Galaxy.