Program: GN-2008A-Q-45

We propose to complete high-resolution observations of 107 members of the Upper Scorpius star-forming region using ALTAIR/NIRI to resolve new multiple systems and search for substellar companions. These observations will allow us to verify many predictions of star formation models: the fractions of binaries and high-order multiples, their dependence on stellar mass, the dependence of companion masses on separation, the fraction of singles/binaries with close or distant BD companions, and the evolution of multiplicity with time. Also, these observations will be complemented by our radial velocity observations of a subset of the sample, allowing us to extend our sensitivity to companions with smaller orbital separations. Furthermore, as all of our targets have been observed with Spitzer, our results will allow us to study the connection between circumstellar disks and stellar multiplicity and/or the presence of substellar companions. Owing to improved resolution (>2X) and sensitivity (>16X) compared to previous work on this region, our observations are bound to uncover many new binaries and high-order multiples, and possibly some substellar companions.