Near infrared and the inner regions of protoplanetary disks

Abstract

We examine the ``puffed-up inner disk'' model (Dullemond, Dominik & Natta 2001), proposed for explaining the near-IR excess radiation from Herbig Ae/Be stars. Detailed model computations show that the observed near-IR excess requires more hot dust than is contained in the puffed-up disk rim. The rim can produce the observed near-IR excess only if its dust has perfectly gray opacity, but such dust is in conflict with the observed 10$\mu$m spectral feature. We find that a compact ($\sim$ 10 AU) tenuous ($\tau_V \la 0.4$) dusty halo around the disk inner regions contains enough dust to readily explain the observations. Furthermore, this model also resolves the puzzling relationship noted by Monnier and Millan-Gabet (2002) between luminosity and the interferometric inner radii of disks.