event
Wednesday 13 Oct 2010: Photoevaporation: A dominant dispersal mechanism of discs
James Owen - IoA, University of Cambridge, UK
Physics, 4th Floor interaction area 11:00-12:00
The evolution of protoplanetary discs, which contain the reservoir of material available for planet formation, is heavily influenced by heating and irradiation from the central star - from IR to X-ray. In fact, X-ray photoevaporation has been suggested as the leading dispersal mechanism. In this talk I will present results from a disc population synthesis model, including only viscous evolution and X-ray photoevaporation. This model suggests that the current observations of disc evolution can be explained using this simple model, with a single set of initial conditions (i.e. initial disc mass, viscous time-scale and viscous alpha parameters). Furthermore, I will show that the X-ray photoevaporation model can now explain observations of many accreting transition discs. These accreting transition discs arrise after photoevaporation opens a gap in the dust and gas disc. The inner disc then drains onto the central star, becoming optically thin due to dust drag on a time-scale much shorter than the draining time-scale. The model predicts that accreting transition discs with accretion rates < 10^-8 Msol yr-1, inner holes with radii < 20 AU and disc masses spanning the observed range of disc masses are consistent with the photoevaporation scenario. Finally, I will discuss some of the direct observable signatures of a photoevaporative wind, and their consistency with the model.
