6 - Near-infrared spectroscopy of stripped-envelope supernovae

Summary

Abstract

Near-infrared (NIR) spectroscopy of several stripped-envelope core-collapse supernovae (SNe) are presented. NIR spectra of these objects are quite rich, exhibiting a large number of emission features. Particularly important are strong lines of He I and C I, which probe the outermost ejecta and constrain the pre-collapse mass-loss. Interestingly, the SN 1998bw-like broad-line Type Ic SN 2002ap does not exhibit the strong C I features seen in other Type Ic SNe. NIR spectra also exhibit strong, relatively isolated lines of Mg I, Si I, Ca II, and O I that provide clues into the kinematics and mixing in the ejecta. Finally, late-time NIR spectra of two Type Ic events: SN 2000ew and SN 2002ap show strong first-overtone carbon monoxide (CO) emission, providing the first observational evidence that molecule formation may not only be common in Type II SNe, but perhaps in all core-collapse events.

Introduction

Near-infrared (NIR) spectroscopy is a powerful tool for the study of supernovae (SNe), offering new insights into the kinematic, chemical, and evolutionary properties of these events. Here we present applications of NIR spectroscopy for the study of three stripped-envelope supernovae, the Type Ib SN 2001B, the Type Ic SN 2000ew and the broad-line Type Ic SN 2002ap. All of the data presented here were obtained using TIFKAM on the 2.4 m Hiltner telescope at MDM Observatory, except for the SN 2002ap data set which also includes spectra obtained at Lick Observatory, IRTF, and Subaru. The reduced spectra are presented in Figures 6.1–6.3.