34th Meeting of the AAS Division on Dynamical Astronomy, May 2003
12 Migration and Others
Oral, Wednesday, May 7, 2003, 10:50am-12:35pm,

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[12.06] Diversity and Origin of 2:1 Orbital Resonances in Extrasolar Planetary Systems

M.H. Lee, S.J. Peale (UCSB)

The 2:1 orbital resonances of the two planets about GJ 876 can be easily established by the differential migration of the orbits due to planet-disk interactions. A wide variety of stable 2:1 resonance configurations can be reached by differential migration of planets on initially coplanar and nearly circular orbits. These include configurations with librations of \theta1 = \lambda1 - 2\lambda2 + \varpi1 (where \lambdai and \varpii are the mean longitudes and the longitudes of periapse) about 0\circ and \theta2 = \lambda1 - 2\lambda2 + \varpi2 about 180\circ (as in the Io-Europa pair), configurations with librations of both \theta1 and \theta2 about 0\circ (as in the GJ 876 system), and configurations with asymmetric librations of \theta1 and \theta2 tens of degrees from either 0\circ or 180\circ. There are however stable resonance configurations with symmetric or asymmetric librations that cannot be reached by capture into resonances by coplanar differential migration. A particular example is the \theta1 = 180\circ and \theta2 = 0\circ configuration with planets on intersecting orbits. If real systems with these configurations are ever found, their origin would require either a migration scenario involving inclination resonances or multiple-planet scattering in crowded planetary systems.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.