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Low-Mass Tertiary Companions to Spectroscopic Binaries I: Common Proper Motion Survey for Wide Companions using 2MASS

We report the first results of a multi-epoch search for wide (separations greater than a few tens of AU), low-mass tertiary companions of a volume-limited sample of 118 known spectroscopic binaries within 30 pc of the Sun, using the 2MASS Point Source Catalog and follow-up observations with the KPNO and CTIO 4m telescopes. Note that this sample is not volume-complete but volume-limited, and, thus, there is incompleteness in our reported companion rates. We are sensitive to common proper motion companions with separations from roughly 200 AU to 10,000 AU (~10" -> ~10'). From 77 sources followed-up to date, we recover 11 previously known tertiaries, three previously known candidate tertiaries, of which two are spectroscopically confirmed and one rejected, and three new candidates, of which two are confirmed and one rejected. This yields an estimated wide tertiary fraction of 19.5^+5.2%_-3.7%. This observed fraction is consistent with predictions set out in star formation simulations where the fraction of wide, low-mass companions to spectroscopic binaries is >10%, and is roughly twice the wide companion rate of single stars.