Planet migration in wind-fed accretion discs in binaries
Planet migration originally refers to protoplanetary discs, which are more massive and dense than typical accretion discs in binary systems. We study planet migration in an accretion disc in a binary system consisting of a solar-like star hosting a planet and a red giant donor star. The accretion disc is fed by a stellar wind. We use the α-disc model and consider that the stellar wind is time dependent. Assuming the disc is quasi-stationary we calculate its temperature and surface density profiles. In addition to the standard disc model, when matter is captured by the disc at its outer edge, we study the situation when the stellar wind delivers matter on the whole disc surface inside the accretion radius with the rate depending on distance from the central star. Implying that a planet experiences classical type I/II migration we calculate migration time for a planet on a circular orbit coplanar with the disc. Potentially, rapid inward planet migration can result in a planet-star merger which can be accompanied by an optical or/and UV/X-ray transient. We calculate time-scale of migration for different parameters of planets and binaries. Our results demonstrate that planets can fall on their host stars within the lifetime of the late-type donor for realistic sets of parameters.