Context :

Aims : We present the implementation of a radiative transfer solver with coherent scattering in the new BIFROST code for radiative magneto-hydrodynamical ( MHD ) simulations of stellar surface convection .
The code is fully parallelized using MPI domain decomposition , which allows for large grid sizes and improved resolution of hydrodynamical structures .
We apply the code to simulate the surface granulation in a solar-type star , ignoring magnetic fields , and investigate the importance of coherent scattering for the atmospheric structure .

Methods : A scattering term is added to the radiative transfer equation , requiring an iterative computation of the radiation field .
We use a short-characteristics-based Gauss-Seidel acceleration scheme to compute radiative flux divergences for the energy equation .
The effects of coherent scattering are tested by comparing the temperature stratification of three 3D time-dependent hydrodynamical atmosphere models of a solar-type star : without scattering , with continuum scattering only , and with both continuum and line scattering .

Results : We show that continuum scattering does not have a significant impact on the photospheric temperature structure for a star like the Sun .
Including scattering in line-blanketing , however , leads to a decrease of temperatures by about 350 K below \log _ { 10 } \tau _ { 5000 } \lesssim - 4 .
The effect is opposite to that of 1D hydrostatic models in radiative equilibrium , where scattering reduces the cooling effect of strong LTE lines in the higher layers of the photosphere .
Coherent line scattering also changes the temperature distribution in the high atmosphere , where we observe stronger fluctuations compared to a treatment of lines as true absorbers .

Conclusions :