The Berkeley sample of stripped-envelope supernovae

We present the complete sample of stripped-envelope supernova (SN) spectra\nobserved by the Lick Observatory Supernova Search (LOSS) collaboration over the\nlast three decades: 888 spectra of 302 SNe, 652 published here for the first\ntime, with 384 spectra (of 92 SNe) having photometrically-determined phases.\nAfter correcting for redshift and Milky Way dust reddening and reevaluating the\nspectroscopic classifications for each SN, we construct mean spectra of the\nthree major spectral subtypes (Types IIb, Ib, and Ic) binned by phase. We\ncompare measures of line strengths and widths made from this sample to the\nresults of previous efforts, confirming that O I {\\lambda}7774 absorption is\nstronger and found at higher velocity in Type Ic SNe than in Types Ib or IIb\nSNe in the first 30 days after peak brightness, though the widths of nebular\nemission lines are consistent across subtypes. We also highlight newly\navailable observations for a few rare subpopulations of interest.\n