  Recent detection of gravitational waves from a binary-neutron star merger
(GW170817) and the subsequent observations of electromagnetic counterparts
provide a great opportunity to study the physics of compact binary mergers. The
optical and near-infrared counterparts to GW170817 (SSS17a, also known as AT
2017gfo or DLT17ck) are found to be consistent with a kilonova/macronova
scenario with red and blue components. However, in most of previous studies in
which contribution from each ejecta component to the lightcurves is separately
calculated and composited, the red component is too massive as dynamical ejecta
and the blue component is too fast as post-merger ejecta. In this letter, we
perform a 2-dimensional radiative transfer simulation for a kilonova/macronova
consistently taking the interplay of multiple ejecta components into account.
We show that the lightcurves and photospheric velocity of SSS17a can be
reproduced naturally by a setup consistent with the prediction of the
numerical-relativity simulations.
