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Samples of reliably identified halo wide binaries are scarce. If reasonablyfree from selection effects and with a small degree of contamination by chancealignments, these wide binaries become a powerful dynamical tool, havingprovided one of the very few experiments capable of constraining the nature ofdark matter in the Milky Way halo. Currently, however, the best availablesample of halo wide binaries is confined to the solar neighborhood, and isplagued by small number statistics at the widest separations. We present theresults of a program aimed to probe the wide binary population of the Galactichalo at significantly larger distances, and which informs future searches thatcould improve the statistics by orders of magnitude. Halo stars were taken fromthe Sloan Digital Sky Survey after analysing the Galactic orbits of stars inthe reduced proper motion diagram. We then select candidate binaries bysearching for pairs with small differences in proper motion and small projectedseparation on the sky. Using medium-resolution spectroscopy, a subsample ofcandidates is validated via radial velocities, finding that about 68\% ofcandidate pairs up to 20$^{\prime\prime}$ separation can be considered genuinehalo wide binaries, to the limits of the available data. Precise parallaxesfrom \textit{Gaia} confirm that most of our selected pairs have theircomponents at the same distances, independently confirming the robustness ofour selection method. These results should prove valuable to guide the optimalassembly of larger catalogs of halo wide binaries from upcoming largedatabases, e.g., \textit{Gaia} and LSST.

A Distant Sample of Halo Wide Binaries from SDSS