The Carnegie Supernova Project-I. Spectroscopic analysis of stripped-envelope supernovae

An analysis leveraging 170 optical spectra of 35 stripped-envelope (SE)core-collapse supernovae observed by the Carnegie Supernova Project-I andpublished in a companion paper is presented. Mean template spectra areconstructed for the SNe IIb, Ib and Ic sub-types and parent ions associatedwith designated spectral features are identified with the aid of the spectralsynthesis code SYNAPPS. Our modeled mean spectra suggest the ~6150 Å featurein SNe~IIb may have an underlying contribution due to silicon, while the samefeature in some SNe Ib may have an underlying contribution due to hydrogen.Standard spectral line diagnostics consisting of pseudo-equivalent widths (pEW)and blue-shifted Doppler velocity are measured for each of the spectralfeatures. Correlation matrices and rolling mean values of both spectraldiagnostics are constructed. A Principle Component Analysis (PCA) is applied tovarious wavelength ranges of the entire data set and suggests clear separationamong the different SE SN sub-types, which follows from trends previouslyidentified in the literature. In addition, our finds reveal the presence of twoSNe IIb sub-types, a handful of SNe Ib displaying signatures of weak,high-velocity hydrogen, and a single SN~Ic with evidence of weak heliumfeatures. Our PCA results can be leveraged to obtain robust sub-typing of SE SNbased on a single spectrum taken during the so-called photospheric phase,separating SNe IIb from SNe Ib with ~80 percent completion.