A1 Refereed original research article in a scientific journal

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




AuthorsHolmbo S., Stritzinger M.D., Karamehmetoglu E., Burns C.R., Morrell N., Ashall C., Hsiao E.Y., Galbany L., Folatelli G., Phillips M.M., Baron E., Gutiérrez C.P., Leloudas G., Müller-Bravo T.E., Hoeflich P., Taddia F., Suntzeff N.B.

PublisherEDP Sciences

Publication year2023

JournalAstronomy and Astrophysics

Article numberA83

Volume675

eISSN1432-0746

DOIhttps://doi.org/10.1051/0004-6361/202245334

Web address https://doi.org/10.1051/0004-6361/202245334

Self-archived copy’s web addresshttps://research.utu.fi/converis/portal/detail/Publication/180598214


Abstract

An analysis leveraging 170 optical spectra of 35 stripped-envelope (SE) core-collapse supernovae (SNe) observed by the Carnegie Supernova Project I and published in a companion paper is presented. Mean template spectra were constructed for the SNe IIb, Ib, and Ic subtypes, and parent ions associated with designated spectral features are identified with the aid of the spectral synthesis code SYNAPPS. Our modeled mean spectra suggest the ~6150 Å feature in SNe IIb may have an underlying contribution due to silicon, while the same feature in some SNe Ib may have an underlying contribution due to hydrogen. Standard spectral line diagnostics consisting of pseudo-equivalent widths (pEWs) and blue-shifted Doppler velocity were measured for each of the spectral features. Correlation matrices and rolling mean values of both spectral diagnostics were constructed. A principle component analysis (PCA) was applied to various wavelength ranges of the entire dataset and suggests clear separation among the different SE SN subtypes, which follows from trends previously identified in the literature. In addition, our findings reveal the presence of two SNe IIb subtypes, a select number of SNe Ib displaying signatures of weak, high-velocity hydrogen, and a single SN Ic with evidence of weak helium features. Our PCA results can be leveraged to obtain robust subtyping of SE SNe based on a single spectrum taken during the so-called photospheric phase, separating SNe IIb from SNe Ib with ~80% completion.


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