Evolution of circumbinary protoplanetary disks with photoevaporative
  winds driven by External Far Ultraviolet Radiation
  Lifetimes of protoplanetary disks (PPDs) are believed to be severely
constrained by material depleting mechanisms, including photoevaporative winds
due to the host star radiation or external radiation sources. Most previous
studies focused on exploring the role of the winds in the exposed PPDs with a
single star; however, exploring the evolution of the circumbinary disks with
the photoevaporative winds driven by the host star radiation and external
radiation sources deserves further investigation. In this study, we investigate
the evolution of the circumbinary PPDs with the photoevaporative winds induced
by external far ultraviolet (FUV) radiation field. We show that this mass-loss
process can significantly constrain properties of a circumbinary PPD, including
its lifetime, mass and radius. The lifetime of a circumbinary PPD, for
instance, is found by a factor of about two longer than a similar circumstellar
disk and this enhancement strongly depends on the viscosity parameter. But our
model shows that viscosity dependence of the disk lifetime in the circumbinary
case is more pronounced compared to the circumstellar case. We also show that
dispersal of a circumbinary PPD occurs over a longer time as the disk
temperature distribution becomes steeper. Our results also imply that dead zone
in a photoevaporative circumbinary PPD extends over a larger radial range in
comparison to a circumstellar disk counterpart. We also show that our
calculations are in agreement with the observed circumbinary PPDs orbiting
equal-mass binaries.
