  In this paper we study the evolution of viscous and radiative circumstellar
disks under the influence of a companion star. We focus on the eccentric
{\gamma} Cephei and {\alpha} Centauri system as examples and compare the disk
quantities such as disk eccentricity and precession rate to previous isothermal
simulations. We perform two-dimensional hydrodynamical simulations of the
binary star systems under the assumption of coplanarity of the disk, host star
and binary companion. We use the grid-based, staggered mesh code FARGO with an
additional energy equation to which we added radiative cooling based on opacity
tables. The eccentric binary companion perturbs the disk around the primary
star periodically. Upon passing periastron spirals arms are induced that wind
from the outer disk towards the star. In isothermal simulations this results in
disk eccentricities up to {\epsilon}_disk ~ 0.2, but in more realistic
radiative models we obtain much smaller eccentricities of about {\epsilon}_disk
~ 0.04 - 0.06 with no real precession. Models with varying viscosity and disk
mass indicate show that disks with less mass have lower temperatures and higher
disk eccentricity. The rather large high disk eccentricities, as indicated in
previous isothermal disk simulations, implied a more difficult planet formation
in the {\gamma} Cephei system due to the enhanced collision velocities of
planetesimals. We have shown that under more realistic conditions with
radiative cooling the disk become less eccentric and thus planet formation may
be made easier. However, we estimate that the viscosity in the disk has to very
small, with {\alpha} \lesssim 0.001, because otherwise the disk's lifetime will
be too short to allow planet formation to occur along the core instability
scenario. We estimate that the periodic heating of the disk in eccentric
binaries will be observable in the mid-IR regime.
