Asphericity in Supernova Explosions from Late-Time Spectroscopy
Keiichi Maeda,1,2,3*
Koji Kawabata,4
Paolo A. Mazzali,2,5,6
Masaomi Tanaka,7
Stefano Valenti,8,9
Ken'ichi Nomoto,1,6,7
Takashi Hattori,10
Jinsong Deng,11
Elena Pian,5
Stefan Taubenberger,2
Masanori Iye,12
Thomas Matheson,13
Alexei V. Filippenko,14
Kentaro Aoki,10
George Kosugi,15
Youichi Ohyama,16
Toshiyuki Sasaki,10
Tadafumi Takata17
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.
1 Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwa-no-ha 5-1-5, Kashiwa City, Chiba 277-8582, Japan.
2 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany.
3 Department of Earth Science and Astronomy, College of Arts and Science, University of Tokyo, Tokyo 153-8902, Japan.
4 Hiroshima Astrophysical Science Center, Hiroshima University, Hiroshima 739-8526, Japan.
5 National Institute for Astrophysics–Osservatorio Astronomica di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy.
6 Research Center for the Early Universe, School of Science, University of Tokyo, Tokyo 113-0033, Japan.
7 Department of Astronomy, School of Science, University of Tokyo, Tokyo 113-0033, Japan.
8 Department of Physics, University of Ferrara, I-44100 Ferrara, Italy.
9 European Organization for Astronomical Research in the Southern Hemisphere, Karl-Schwarzschild-Strasse 1, 85741 Garching, Germany.
10 Subaru Telescope, National Astronomical Observatory of Japan (NAOJ), 650 North A'ohoku Place, Hilo, HI 96720, USA.
11 National Astronomical Observatory, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, China.
12 Division of Optical and Infrared Astronomy, NAOJ, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan.
13 National Optical Astronomy Observatory, Tucson, AZ 85719, USA.
14 Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA.
15 Atacama Large Millimeter/Submillimeter Array Project, NAOJ, Mitaka, Tokyo 181-8588, Japan.
16 Department of Infrared Astrophysics, Institute of Space and Astronomical Science, Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan.
17 Astronomy Data Center, NAOJ, Mitaka, Tokyo 181-8588, Japan.
* To whom correspondence should be addressed. E-mail: maeda{at}ea.c.u-tokyo.ac.jp
