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We present the results of hydrodynamical simulations of the orbital evolutionof planets undergoing runaway gas accretion in radiative discs. We consideraccreting disc models with constant mass flux through the disc, and whereradiative cooling balances the effect of viscous heating and stellarirradiation. We assume that 20-30 $M_\oplus$ giant planet cores are formed inthe region where viscous heating dominates and migrate outward under the actionof a strong corotation torque. In the case where gas accretion is neglected, wefind evidence for strong dynamical torques in accreting discs with accretionrates ${\dot M}\gtrsim 7\times 10^{-8} \;M_\odot/yr$. Their main effect is toincrease outward migration rates by a factor of $\sim 2$ typically. In thepresence of gas accretion, however, runaway outward migration is observed withthe planet passing through the zero-torque radius and the transition betweenthe viscous heating and stellar heating dominated regimes. The ability for anaccreting planet to enter a fast migration regime is found to depend stronglyon the planet growth rate, but can occur for values of the mass flux throughthe disc of ${\dot M}\gtrsim 5\times 10^{-8} \;M_\odot/yr$. We find that anepisode of runaway outward migration can cause an accreting planet formed inthe 5-10 AU region to temporarily orbit at star-planet separations as large as$\sim$60-70 AU. However, increase in the amplitude of the Lindblad torqueassociated with planet growth plus change in the streamline topology near theplanet systematically cause the direction of migration to be reversed. Ourresults indicate that a planet can reach large orbital distances under thecombined effect of dynamical torques and gas accretion, but an alternativemechanism is required to explain the presence of massive planets on wideorbits.

Migration of accreting planets in radiative discs from dynamical torques