DETECTION OF A MOLECULAR DISK ORBITING THE NEARBY, OLD, CLASSICAL T TAURI STAR MP MUSCAE

We have used the Atacama Pathfinder Experiment 12 m telescope to detect circumstellar CO emission from MP Muscae (MP Mus; K1 IVe), a nearby (D similar to 100 pc), actively accreting, similar to 7 Myr old pre-main-sequence (pre-MS) star. The CO emission line profile measured for MP Mus is indicative of an orbiting disk with radius similar to 120 AU, assuming that the central star mass is 1.2M circle dot and the disk inclination is i similar to 30 degrees. The inferred disk molecular gas mass is similar to 3M circle plus. MP Mus thereby joins TW Hya and V4046 Sgr as the only late-type (low-mass), pre-MS star systems within similar to 100 pc of Earth that are known to retain orbiting, molecular disks.We also report the nondetection (with the Institut de Radio Astronomie Millimetrique 30 m telescope) of CO emission from another 10 nearby (D less than or similar to 100 pc), dusty, young (age similar to 10-100 Myr) field stars of spectral type A-G. We discuss the implications of these results for the timescales for stellar and Jovian planet accretion from, and dissipation of, molecular disks around young stars.