A New Brown Dwarf Desert? A Scarcity of Wide Ultracool Binaries

Abstract

We present the results of a deep-imaging search for wide companions to low-mass stars and brown dwarfs using NSFCam on IRTF. We searched a sample of 132 M7-L8 dwarfs to magnitude limits of $J\sim 20.5$ and $K\sim 18.5$, corresponding to secondary-primary mass ratios of $\sim 0.5$. No companions were found with separations between $2{\arcsec}$ to $31{\arcsec}$ ($\sim$40 AU to $\sim$1000 AU). This null result implies a wide companion frequency below 2.3% at the 95% confidence level within the sensitivity limits of the survey. Preliminary modeling efforts indicate that we could have detected 85% of companions more massive than $0.05M_{\odot }$ and 50% above $0.03M_{\odot }$.

27 pages, 8 figures, 3 tables: accepted to the Astronomical Journal

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