  We study the evolution of an embedded protoplanet in a circumstellar disk
using the 3D-Radiation Hydro code TRAMP, and treat the thermodynamics of the
gas properly in three dimensions. The primary interest of this work lies in the
demonstration and testing of the numerical method. We show how far numerical
parameters can influence the simulations of gap opening. We study a standard
reference model under various numerical approximations. Then we compare the
commonly used locally isothermal approximation to the radiation hydro
simulation using an equation for the internal energy. Models with different
treatments of the mass accretion process are compared. Often mass accumulates
in the Roche lobe of the planet creating a hydrostatic atmosphere around the
planet. The gravitational torques induced by the spiral pattern of the disk
onto the planet are not strongly affected in the average magnitude, but the
short time scale fluctuations are stronger in the radiation hydro models.
  An interesting result of this work lies in the analysis of the temperature
structure around the planet. The most striking effect of treating the
thermodynamics properly is the formation of a hot pressure--supported bubble
around the planet with a pressure scale height of H/R ~ 0.5 rather than a thin
Keplerian circumplanetary accretion disk. We also observe an outflow of gas
above and below the planet during the gap opening phase.
