Year: 2009
Type: article
Abstract: The velocity of the inner ejecta of stripped-envelope core-collapse supernovae (CC-SNe) is studied by means of an analysis of their nebular spectra. Stripped-envelope CC-SNe are the result of the explosion of bare cores of massive stars (≥8 M⊙), and their late-time spectra are typically dominated by a strong [O i]λλ6300, 6363 emission line produced by the innermost, slow-moving ejecta which are not visible at earlier times as they are located below the photosphere. A characteristic velocity of the inner ejecta is obtained for a sample of 56 stripped-envelope CC-SNe of different spectral types (IIb, Ib, Ic) using direct measurements of the linewidth as well as spectral fitting. For most SNe, this value shows a small scatter around 4500 km s−1. Observations (<100 d) of stripped-envelope CC-SNe have revealed a subclass of very energetic SNe, termed broad-lined SNe (BL-SNe) or hypernovae, which are characterized by broad absorption lines in the early-time spectra, indicative of outer ejecta moving at very high velocity (v≥ 0.1c). SNe identified as BL in the early phase show large variations of core velocities at late phases, with some having much higher and some having similar velocities with respect to regular CC-SNe. This might indicate asphericity of the inner ejecta of BL-SNe, a possibility we investigate using synthetic three-dimensional nebular spectra.
Institutions: Max Planck Society, Max Planck Institute for Astrophysics, Chinese Academy of Sciences, National Astronomical Observatories, University of California, Berkeley, University of Chile, Center for Astrophysics Harvard & Smithsonian, NSF NOIRLab, European Southern Observatory, Trieste Astronomical Observatory, National Institute for Astrophysics, University of Copenhagen, Carnegie Observatories, Las Campanas Observatory
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W1928043958