Spiral waves triggered by shadows in transition disks
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Circumstellar asymmetries such as central warps have recently been shown to cast shadows on outer disks. We investigate the hydrodynamical consequences of such variable illumination on the outer regions of a transition disk, and the development of spiral arms. Using 2D simulations, we follow the evolution of a gaseous disk passively heated by the central star, under the periodic forcing of shadows with an opening angle of similar to 28 degrees. With a lower pressure under the shadows, each crossing results in a variable azimuthal acceleration, which in time develops into spiral density waves. Their pitch angles evolve from Pi similar to 15 degrees-22 degrees at the onset, to similar to 11 degrees-14 degrees, over similar to 65 au to 150 au. Self-gravity enhances the density contrast of the spiral waves, as also reported previously for spirals launched by planets. Our control simulations with unshadowed irradiation do not develop structures, except for a different form of spiral waves seen at later times only in the gravitationally unstable control case. Scattered light predictions in the H-band show that such illumination spirals should be observable. We suggest that spiral arms in the case-study transition disk HD 142527 could be explained as a result of shadowing from the tilted inner disk.
Millennium Nucleus grant RC130007 CONICYT-Gemini grant 32130007 FONDECYT 1130949 3140601 1141175
Artículo de publicación ISI
Quote ItemThe Astrophysical Journal Letters, 823:L8 (6pp), 2016 May 20
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