  Recently, a number of planets orbiting binary stars have been discovered by
the Kepler space telescope. In a few systems the planets reside close to the
dynamical stability limit. Due to the difficulty of forming planets in such
close orbits, it is believed that they have formed further out in the disk and
migrated to their present locations. Our goal is to construct more realistic
models of planet migration in circumbinary disks, and to determine the final
position of these planets. In our work, we focus on the system Kepler-38. The
evolution of the circumbinary disk is studied using two-dimensional
hydrodynamical simulations. We study locally isothermal disks as well as more
realistic models with viscous heating, radiative cooling from the disk
surfaces, and radiative diffusion in the disk mid plane. After the disk has
been brought into equilibrium, a 115 Earth-mass planet is embedded and its
evolution is followed. In all cases the planets stop inward migration near the
inner edge of the disk. In isothermal disks with a typical disk scale height of
H/r = 0.05, the final outcome agrees very well with the observed location of
planet Kepler-38b. For the radiative models, the disk thickness and location of
the inner edge is determined by the mass in the system. For surface densities
in the order of 3000 g/cm^2 at 1 AU, the inner gap lies close to the binary and
planets stop in the region between the 5:1 and 4:1 mean-motion resonances with
the binary. A model with a disk with approximately a quarter of the mass yields
a final position very close to the observed one. For planets migrating in
circumbinary disks, the final position is dictated by the structure of the
disk. Knowing the observed orbits of circumbinary planets, radiative disk
simulations with embedded planets can provide important information on the
physical state of the system during the final stages of its evolution.
