THE DISPERSAL OF PROTOPLANETARY DISKS AROUND BINARY STARS

I present models of disk evolution around young binary stars. I show that the primary factor in determining circumbinary disk lifetimes is the rate of disk photoevaporation. I also find that photoevaporative clearing leaves a signature on the distribution of circumbinary disk lifetimes, with a sharp increase in disk lifetimes for binary separations a ≲ 0.3–1 AU. Observations of young binary stars can therefore be used to test models of disk evolution, and I show that current data set a strong upper limit to the rate of on-going photoevaporation (<10 −9 M ☉ yr −1 ). Finally I discuss the implications of these results for planet formation and suggest that circumbinary planets around close ( a ≲ 1 AU) binaries should be relatively common.