  The process of migration into resonance capture has been well studied for
planetary systems where the gravitational potential is generated exclusively by
the star and planets. However, massive protoplanetary disks add a significant
perturbation to these models. In this paper we consider two limiting cases of
disk-induced precession on migrating planets and find that small amounts of
precession significantly affect the equilibrium reached by migrating planets.
We investigate these effects with a combination of semi-analytic models of the
resonance and numerical integrations. We also consider the case of the disk's
dispersal, which can excite significant libration amplitude and can cause
ejection from resonance for large enough precession rates. Both of these
effects have implications for interpreting the known exoplanet population and
may prove to be important considerations as the population of
well-characterized exoplanet systems continues to grow.
