Statistical Analysis of Early Spectra in Type II and IIb Supernovae

We present a new observational method to distinguish type II (SNe II) from type IIb supernova (SNe IIb) at early times. Using public spectroscopic data of 196 SNe II and 204 SNe IIb, we analysed H𝛼 and the He I 5876 at early phases (< 40 days from the explosion) to test possible differences between these two SN types. By comparing the pseudo-equivalent width (pEW) and full width at half maximum (FWHM), we find that the strength of the H𝛼 and He I lines can be used to establish those differences quantitatively, being the lines of SNe IIb stronger at all times. Additionally, we will use statistical and analytical tools to prove the significance of these observed differences.