Hunting for Long-lived Protoplanetary Disks Observed with AKARI/FIS

Twenty-one YSO (Young Stellar Object) candidates nearby the solar system have been identified through cross-correlating Hipparcos (High Precision Parallax Collecting Satellite) catalog with the AKARI/FIS YSO catalog, and the reliability is over 90%. The central objects cover the spectral types from B to M. The Hipparcos's accurate measurements of trigonometric parallaxes enable us to place these objects in the H-R diagram, which can be used to determine their ages by the isochrones of theoretical evolution trajectories. In this sample, two YSOs have been found to be older than 10 Myr. The spectral energy distributions (SEDs) from optical to infrared show that the two YSOs belong to the type II YSOs with protoplanetary disks. Furthermore, from the SED fitting, the ages of these two sources are constrained to be (14.1±4.2) Myr and (16.8±4.4) Myr, respectively. Therefore, two YSO candidates with long-lived protoplanetary disks have been detected in the AKARI/FIS data. The long-lived protoplanetary disks are closely related with the planet formation, and they are ideal birthplaces of protoplanets.