Asphericity in Supernova Explosions from Late-Time Spectroscopy
2008
Maeda, Keiichi | Kawabata, Koji | Mazzali, Paolo A. | Tanaka, Masaomi | Valenti, Stefano | Nomoto, Ken'ichi | Hattori, Takashi | Deng, Jinsong | Pian, Elena | Taubenberger, Stefan | Iye, Masanori | Matheson, Thomas | Filippenko, Alexei V. | Aoki, Kentaro | Kosugi, George | Ohyama, Youichi | Sasaki, Toshiyuki | Takata, Tadafumi
Core-collapse supernovae (CC-SNe) are the explosions that announce the death of massive stars. Some CC-SNe are linked to long-duration gamma-ray bursts (GRBs) and are highly aspherical. One important question is to what extent asphericity is common to all CC-SNe. Here we present late-time spectra for a number of CC-SNe from stripped-envelope stars and use them to explore any asphericity generated in the inner part of the exploding star, near the site of collapse. A range of oxygen emission-line profiles is observed, including a high incidence of double-peaked profiles, a distinct signature of an aspherical explosion. Our results suggest that all CC-SNe from stripped-envelope stars are aspherical explosions and that SNe accompanied by GRBs exhibit the highest degree of asphericity.
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