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D. Lai (Cornell Univ.), H. Zhang (Cornell Univ. and NJNU)
We study the excitation of density and bending waves and the associated angular momentum transfer in a circumstellar disk by a binary companion or a planet. This is important for determining the apparence and secular evolution of the disk and/or palnet/companion. Unlike previous analytic works, our disks are three-dimensional and have finite thickness, and we are able to treat both the spiral density waves and bending waves in a unified way. In a 3D disk, waves are excited at both Lindblad resonances and vertical resonances. The torque on the disk is positive for waves excited at outer Linblad/vertical resonances and negative at inner Lindblad/vertical resonances. We have derived new analytical expressions for the amplitudes of different wave modes excited at Lindblad and/or vertical resonances and the resulting torques on the disk. It is found that under certain conditions, angular momentum transfer through vertical resonances is much more efficient than Lindblad resonances. This implies that in some situations (e.g., a circumstellar disk perturbed by a planet in an inclined orbit), vertical resonances may be the dominant channel of angular momentum transfer between the disk and the external potential. We have also derived new formulae for the angular momentum dissipation at corotation and studied wave excitations at disk boundaries.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.