ASASSN-13dn light curve. A secondary peak is observed ∼73 days after the first detection. In the tail of the light curve, clear signs of ejecta-CSM interaction are seen in the wiggles. The decline in slope after the secondary peak is faster than the decline after the first peak. The lines at the bottom mark the epochs where spectroscopic data are available. The vertical lines divide the light curve into the phases described in Sect. 3.1.