Type II Supernova Spectral Diversity. I. Observations, Sample Characterization, and Spectral Line Evolution

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...

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Bibliographic Details
Authors: Gutiérrez, Claudia P., Anderson, Joseph P., Hamuy, Mario, Morrell, Nidia Irene, González Gaitan, Santiago, Stritzinger, Maximilian D., Phillips, Mark M., Galbany, Lluis, Folatelli, Gastón, Dessart, Luc, Contreras, Carlos, Della Valle, Massimo, Freedman, Wendy L., Hsiao, Eric Y., Krisciunas, Kevin, Madore, Barry F., Maza, José, Suntzeff, Nicholas B., Prieto, José Luis, González, Luis, Cappellaro, Enrico, Navarrete, Mauricio, Pizzella, Alessandro, Ruiz, María T., Smith, R. Chris, Turatto, Massimo
Format: article
Status:Published version
Publication Date:2017
Country:Argentina
Institution:Universidad Nacional de La Plata
Repository:SEDICI (UNLP)
Language:English
OAI Identifier:oai:sedici.unlp.edu.ar:10915/87198
Online Access:http://sedici.unlp.edu.ar/handle/10915/87198
Access Level:Open access
Keyword:Ciencias Astronómicas
supernovae: general
surveys
techniques: photometric
techniques: spectroscopic
Description
Summary: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 nondetection constraints for estimating SN explosion epochs. The time evolution of spectral lines is presented and analyzed 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 ∼9600 to ∼1500 km s<sup>-1</sup> at 50 days post-explosion with a median H<sub>α</sub> value of 7300 km s<sup>-1</sup>. This is most likely explained through differing explosion energies. Significant diversity is also observed in the absolute strength of spectral lines, characterized 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 shows an extra absorption component on the blue side of the H<sub>α</sub> 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 ∼35 days) are associated with Si ii λ6355, while past the middle of the plateau phase they are related to high velocity (HV) features of hydrogen lines.

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