Line Identifications of Type I Supernovae: On the Detection of Si II for these Hydrogen-poor Events

Understand

Here we revisit line identifications of type I supernovae and highlight trace amounts of unburned hydrogen as an important free parameter for the composition of the progenitor.

• Most 1-dimensional stripped-envelope models of supernovae indicate that observed features near 6000-6400 Ang in type I spectra are due to more than Si II 6355.
• However, while an interpretation of conspicuous Si II 6355 can approximate 6150 Ang absorption features for all type Ia supernovae during the first month of free expansion, similar identifications applied to 6250 Ang features of type Ib and Ic supernovae have not been as successful.
• When the corresponding synthetic spectra are compared to high quality time-series observations, the computed spectra are frequently too blue in wavelength.