A Keck LGS AO Search for Brown Dwarf and Planetary Mass Companions to Upper Scorpius Brown Dwarfs
Beth Biller, Katelyn Allers, Michael Liu, Laird Close, Trent Dupuy

TL;DR
This study used Keck LGS AO to search for companions to young brown dwarfs in Upper Scorpius, discovering a new binary and constraining the binary fraction among substellar objects, revealing similarities and differences with field populations.
Contribution
First high-resolution adaptive optics survey of young brown dwarfs in Upper Scorpius, providing new binary detections and improved constraints on binary fractions in this population.
Findings
Discovered a 0.14" binary companion to a brown dwarf in Upper Scorpius.
Estimated binary fraction for low-mass brown dwarfs is similar to field T dwarfs.
Medium-separation binaries are more common in young populations than in the field.
Abstract
We searched for binary companions to 20 young brown dwarfs in the Upper Scorpius association (145 pc, 5 Myr, nearest OB association) with the the Laser Guide Star adaptive optics system and the facility infrared camera NIRC2 on the 10 m Keck II telescope. We discovered a 0.14" companion (20.9+-0.4 AU) to the <0.1 MSun object SCH J16091837-20073523. From spectral deconvolution of integrated-light near-IR spectroscopy of SCH1609 using the SpeX spectrograph (Rayner et al. 2003), we estimate primary and secondary spectral types of M6+-0.5 and M7+-1.0, corresponding to masses of 79+-17 MJup and 55+-25 MJup at an age of 5 Myr and masses of 84+-15 MJup and 60+-25 MJup at an age of 10 Myr. For our survey objects with spectral types later than M8, we find an upper limit on the binary fraction of <9% (1-sigma) at separations of 10 -- 500 AU. We combine the results of our survey with previous…
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