  Massive planets that open a gap in the accretion disk are believed to migrate
with exactly the viscous speed of the disk, a regime termed type II migration.
Population synthesis models indicate that standard type II migration is too
rapid to be in agreement with the observations. We study the migration of
massive planets between $2\times10^{-4}$ and $2\times10^{-3} M_\odot$
corresponding to 0.2 to 2 Jupiter masses $M_J$. in order to estimate the
migration rate in comparison to type II migration. We follow the evolution of
planets embedded in two-dimensional, locally isothermal disks with non-zero
mass accretion which is explicitly modelled using suitable in- and outflow
boundary conditions to ensure a specific accretion rate. After a certain
relaxation time we release the planet and measure its migration through the
disk and the dependence on parameters such as viscosity, accretion rate and
planet mass. We study accreting and non-accretion planets. The inferred
migration rate of the planet is determined entirely by the disk torques acting
on it and is completely independent of the viscous inflow velocity, so there is
no classical type II migration regime. Depending on the local disk mass the
migration rate can be faster or slower than type II migration. From the torques
and the accretion rate profile in the disk we see that the gap formed by the
planet does not separate the inner from the outer disk as necessary for type II
migration, rather gas crosses the gap or is accreted onto the planet.
