{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/type-ii-supernova-spectral-diversity-i","title":"Type II supernova spectral diversity I: Observations, sample characterization and spectral line evolution","arxiv_id":"1709.02487","date":"2017-09-07","proceeding":null,"authors":["Claudia P. Gutiérrez","Joseph P. Anderson","Mario Hamuy","Nidia Morrell","Santiago González-Gaitan","Maximilian D. Stritzinger","Mark M. Phillips","Lluis Galbany","Gastón Folatelli","Luc Dessart","Carlos Contreras","Massimo Della Valle","Wendy L. Freedman","Eric Y. Hsiao","Kevin Krisciunas","Barry F. Madore","José Maza","Nicholas B. Suntzeff","Jose Luis Prieto","Luis González","Enrico Cappellaro","Mauricio Navarrete","Alessandro Pizzella","Maria T. Ruiz","R. Chris Smith","Massimo Turatto"],"abstract":"We present 888 visual-wavelength spectra of 122 nearby type II supernovae (SNe II) obtained between 1986 and 2009, and ranging between 3 and 363 days post explosion. In this first paper, we outline our observations and data reduction techniques, together with a characterization based on the spectral diversity of SNe~II. A statistical analysis of the spectral matching technique is discussed as an alternative to non-detection constraints for estimating SN explosion epochs. The time evolution of spectral lines is presented and analysed in terms of how this differs for SNe of different photometric, spectral, and environmental properties: velocities, pseudo-equivalent widths, decline rates, magnitudes, time durations, and environment metallicity. Our sample displays a large range in ejecta expansion velocities, from $\\sim9600$ to $\\sim1500$ km s$^{-1}$ at 50 days post explosion with a median H$_{\\alpha}$ value of 7300 km s$^{-1}$. This is most likely explained through differing explosion energies. Significant diversity is also observed in the absolute strength of spectral lines, characterised through their pseudo-equivalent widths. This implies significant diversity in both temperature evolution (linked to progenitor radius) and progenitor metallicity between different SNe~II. Around 60\\% of our sample show an extra absorption component on the blue side of the H$_{\\alpha}$ P-Cygni profile (\"Cachito\" feature) between 7 and 120 days since explosion. Studying the nature of Cachito, we conclude that these features at early times (before $\\sim35$ days) are associated with \\ion{Si}{2} $\\lambda6355$, while past the middle of the plateau phase they are related to high velocity (HV) features of hydrogen lines.","url_abs":"https://arxiv.org/abs/1709.02487v1","url_pdf":"https://arxiv.org/pdf/1709.02487v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"type-ii-supernova-spectral-diversity-i","repo_url":"https://github.com/MickaelRigault/pysnid","is_official":0,"mentioned_in_paper":0,"mentioned_in_github":1,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}