Kasen (2010) model (dashed lines) for the early light curve of iPTF15dtg, in Bgri-bands. This model describes the emission from the interaction with a companion star. In the modeling, we adopt the ejecta mass and explosion energy derived from the hydrodynamical modeling. We modified the original Kasen (2010), optimized for SNe Ia, to reproduce the interaction of a compact WR star with a companion. Shown by dotted lines is the Bgri emission from the ⁵⁶Ni contribution, as derived from the hydrodynamical modeling. The Kasen (2010) model alone reproduces the B, g, and r-band emission up to +5 d. However, if we also add the ⁵⁶Ni contribution to the model, then there is a mismatch to the data owing to the long timescale of the companion interaction process.