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Astrophysics Colloquium

Planet Signatures in Transitional Disks
Presented by Wladimir Lyra
Jet Propulsion Laboratory, California Institute of Technology

Thursday, May 14, 2015
4:00 P.M. in 169-336

Recently, high angular resolution imaging of the outer regions of transitional disks have become available, showing a plethora of puzzling asymmetries that beg for explanation. The presence of planets is a particularly attractive interpretation for explaining these asymmetries, since they generally match the range of structures predicted by hydrodynamical models of planet-disk interactions. In this talk I will focus on two of these structures, spiral arms and non-axisymmetric dust clouds, that have been seen in images obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and with the Atacama Large Millimeter Array (ALMA). Giant horseshoe-shaped dust distributions have been tentatively explained as dust trapping in giant vortices, akin to Jupiter's Great Red Spot, excited via Kelvin-Helmholtz instability in the gaps walls carved by planets. In this talk I will detail a steady-state solution for the dust trapping. Based on our solution, we derive quantities of observational interest and, applying the model to recently observed systems, find values within the range of the observational uncertainties. For spiral arms, however, comparing the predictions of planet-disk interaction models to the observed features has shown far from perfect agreement. This may be due to the strong approximations used for the predictions. For example, spiral arm fitting typically uses results that are based on low-mass planets in an isothermal gas. I will show how, by relaxing this approximation, spiral wakes of massive protoplanets produce significant shock heating that can trigger buoyant instabilities. The spirals that form in disks heated by these effects are less tightly wound, potentially better fitting the spiral structures observed in transition disks.

SVCP Astrophysics

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