ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Database B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Database O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength I-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
tokens: sample of SNe included in this data release, our adopted classifications and dates of peak brightness (if available), and the values we used to perform redshift and dust-reddening corrections. Table 3 provides a description of the spectra included in our sample. Our research group utilizes a database of observations and associated metadata (the SNDB; Silverman et al. 2012a ) to orchestrate our observational campaigns, to facilitate access to and analysis of our large repository of data, and to share those data publicly – all of the spectra described herein are publicly available through the SNDB web page (see footnote 1). Table 3. The spectra presented in this paper. Notes. (Truncated; full table available online) α Days relative to peak brightness, if date of peak is constrained. β Estimated average resolution across the spectrum. γ Original publications for already-published spectra. δ This historical spectrum was observed under unique conditions – we exclude from our analyses below but we include it here for completeness. The majority of SNe in this sample have only a few spectral observations each, though several well-observed examples of each subtype are also included – Fig. 3 shows the distribution of observation count across SNe in our sample. Our sample includes spectra taken within days of core collapse out to several years [for those SNe that show ongoing, luminous interaction with circumstellar material (CSM)]. Fig. 4 illustrates the phase coverage for spectra of those SNe having either a photometrically or SNID -measured peak-brightness date. Figure 3. The distribution of spectral observation counts for SNe in our sample. Totals are binned over five-spectra intervals, and we group spectra of peculiar subtypes and of stripped-envelope SNe without a clearcut subtype classification together into the ‘other’ category. Figure 4. The phase distribution of spectra having a measured date of peak brightness, grouped by spectral type and binned over 50-d intervals. Spectra having photometric peak dates are shown in solid, while the lighter shade also includes those with snid -determined peak dates. This plot is truncated at 450 days; a small number of observations exist at later phases. 4 RESULTS Below we examine the evolution, relative to date of peak brightness, of several different observational signatures in order to probe the kinematics and composition of the ejecta and to compare to previous results. In summary, we confirm that the O i λ7774 feature has both a higher pseudo-equivalent width (pEW) and a higher characteristic velocity in SNe Ic than in SNe Ib or IIb, supporting the interpretation that SNe Ic are stripped further down toward the C-O core than SNe Ib/IIb but they explode with similar energies. However, we do not find supporting evidence for that scenario from an analysis of the nebular spectra: one may expect that SNe Ic, having lost more of their envelope but exploding at similar energies, would exhibit wider full width at