SN 2016coi/ASASSN-16fp: An example of residual helium in a type Ic supernova?

Understand

The optical observations of Ic-4 supernova (SN) 2016coi/ASASSN-16fp, from $\sim 2$ to $\sim450$ days after explosion, are presented along with analysis of its physical properties.

• The SN shows the broad lines associated with SNe Ic-3/4 but with a key difference.
• The early spectra display a strong absorption feature at $\sim 5400$ \AA\ which is not seen in other SNe~Ic-3/4 at this epoch.
• This feature has been attributed to He I in the literature.