Radiation-induced Warping of Protostellar Accretion Disks

We examine the consequences of radiatively driven warping of accretion diskssurrounding pre-main-sequence stars. These disks are stable against warping ifthe luminosity arises from a steady accretion flow, but are unstable at latetimes when the intrinsic luminosity of the star overwhelms that provided by thedisk. Warps can be excited for stars with luminosities of around 10 solarluminosities or greater, with larger and more severe warps in the more luminoussystems. A twisted inner disk may lead to high extinction towards stars oftenviewed through their disks. After the disk at all radii becomes optically thin,the warp decays gradually on the local viscous timescale, which is likely to belong. We suggest that radiation induced warping may account for the origin ofthe warped dust disk seen in Beta Pictoris, if the star is only around 10-20Myr old, and could lead to non-coplanar planetary systems around higher massstars.Comment: 12 pages, including 3 figures. ApJ Letters, in pres