A coronagraphic search for brown dwarfs and planets around nearby stars

We have started a corongraphic search for brown dwarfs and planets around young nearby stars within 20 pc of the Sun, using the adaptive optics coronagraph, CIAO, on Subaru. The dynamic range we have achieved is Delta K = 13 at 2.5 '' from the central star. For a typical target with K = 7 at 10 pc, the limiting absolute magnitude is M-K = 20. We apply two kinematical age criteria to select M and K dwarfs statistically younger than 350Myr. The first criterion is a small velocity deviation from the velocity of LSR. The second is a (U, V, W) velocity vector similar to a particular young moving group. The combination of the age and magnitude limits implies that the mass limit for giant planet detection is about 2M(J). We show a sample image of a target field at 3 pc of the Sun with faint companion candidates, to be followed up for the common proper motion test. We give a brief description of our procedures for data acquisition, reduction, and analysis.