We present deep 1.2mm photometry of 37 stars in the young (5Myr) Upper Scorpius OB association, sensitive to 4 × 10-3 M Jup of cool millimeter dust. Disks around four low- and solar-mass stars are detected, as well as one debris disk around an intermediate-mass star, with dust masses ranging from 3.6 × 10-3 to 1.0 × 10-1M Jup. The source with the most massive disk exhibits a transition-disk spectral energy distribution. Combining our results with previous studies, we find that the millimeter-detection fraction of ClassII sources has significantly decreased from younger ages, and comparison with near-infrared and Hα measurements indicates that the present disks have undergone significant evolution in composition or structure at all radii. The disks of Upper Scorpius represent the tail-end of the depletion of primordial disks; while a few near-solar-mass stars may still sustain giant planet formation, this process has finished around higher mass stars.
- circumstellar matter
- open clusters and associations: individual (Upper Scorpius OB1)
- protoplanetary disks
- stars: pre-main sequence