  Using the near-infrared spectrometer SpeX and its slit-viewing camera at the
IRTF, I have resolved a low-mass member of the Upper Scorpius OB association
into a double star. From K-band images of the pair, DENIS-P J161833.2-251750.4
A and B, I measure a separation of 0.96" and a magnitude difference of dK=0.42
mag. I present resolved 0.8-2.5 micron spectroscopy of the two objects, both of
which exhibit signatures of youth in the shape of their H- and K-band continua,
demonstrating that both are members of Upper Scorpius rather than field stars.
In addition, through a comparison to optically-classified pre-main-sequence
objects, I derive a spectral type near M5 for each component, corresponding to
a mass of ~0.15 Msun with the evolutionary models of Chabrier and Baraffe. The
probability that this pair is composed of unrelated M-type members of Upper
Scorpius is ~10^-5. When added to the recent discoveries of other wide, easily
disrupted low-mass binaries, this new system further establishes that the
formation of low-mass stars and brown dwarfs does not require ejection from
multiple systems. These observations also indicate that wide low-mass binaries
can form in OB associations as well as in smaller clusters where the previously
known wide pairs have been found. Thus, the available data show no perceptible
effect of star-forming environment on the prevalence of loosely bound low-mass
systems.
