Nature 371, 227 - 229 (15 September 2002); doi:10.1038/371227a0

A carbon–oxygen star as progenitor of the type Ic supernova 1994I

K. Nomoto^*, H. Yamaoka^†, O. R. Pols^‡, E. P. J. van den Heuvel^§, K. Iwamoto^*, S. Kumagai & T. Shigeyama^*

^* Department of Astronomy, School of Science, University of Tokyo, Tokyo 113, Japan
^† Department of Physics, Faculty of Science, Kyushu University, Fukuoka 810, Japan
^‡Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA, UK
^§ Astronomy Institute and Centre for High Energy Astrophysics, University of Amsterdam, Amsterdam, The Netherlands
Institute of Physical and Chemical Research, Wako, Saitama 350-01, Japan

SUPERNOVAE are classified observationally as type I (which have no hydrogen emission lines in their optical spectra) or type II (which do have hydrogen lines), and are further subdivided¹ into types Ia, Ib, Ic, IIP, IIL and IIb. Type II supernovae are generally thought to result from the explosion of massive stars, and type Ia supernovae from white-dwarf stars that have accreted sufficient mass from a companion to trigger explosion^1,2. The origins of types Ib and Ic are much less clear. The Ic class has been particularly controversial, with two main alternatives: the explosion of a massive star that has lost its hydrogen and helium envelopes through fast stellar winds, exposing the carbon- and oxygen-rich core; or the transfer of material to a companion, leaving a small, bare carbon–oxygen (C + O) star which subsequently explodes^3,4. We show here that the observed characteristics of SN1994I (in the nearby galaxy NGC5194), which has recently^5,6 been classified as type Ic, are best understood on the basis of the second of the two alternatives above: that the progenitor was in a close binary system and lost its outer envelopes, leaving a C + O star (of mass 2 solar masses) which exploded when its iron core collapsed.

References

1.	Branch, D., Nomoto, K. & Filippenko, A. V. Comments Astrophys. 15, 221−237 (1991).
2.	Wheeler, J. C. & Harkness, R. P. Rep. Prog. Phys. 53, 1467−1557 (1990). | Article | ChemPort |
3.	Filippenko, A. V., Porter, A. C. & Sargent, W. L. W. Astr. J. 100, 1575−1587 (1990). | Article | ChemPort |
4.	Wheeler, J. C. et al. Astrophys. J. 313, L69−L73 (1987). | Article | ChemPort |
5.	Schmidt, B., Challis, P. & Kirshner, R. IAU Circ. No. 5966 (1994).
6.	Clocchiatti, A., Brotherton, M., Harkness, R. P. & Wheeler, J. C. IAU Circ. No. 5972 (1994).
7.	Woosley, S. E., Langer, N. & Weaver, T. A. Astrophys. J. 411, 823−839 (1993). | Article | ChemPort |
8.	Shigeyama, T., Nomoto, K., Tsujimoto, T. & Hashimoto, M. Astrophys. J. 361, L23−L27 (1990). | Article | ChemPort |
9.	Nomoto, K., Filippenko, A. V. & Shigeyama, T. Astr. Astrophys. 240, L1−L4 (1990). | ChemPort |
10.	Lucy, L. B. Astrophys. J. 383, 308−313 (1991). | Article | ChemPort |
11.	Swartz, D. A., Filippenko, A. V., Nomoto, K. & Wheeler, J. C. Astrophys. J. 411, 313−322 (1993). | Article | ChemPort |
12.	Yamaoka, H., Shigeyama, T. & Nomoto, K. Astr. Astrophys. 267, 433−438 (1993).
13.	Wheeler, J. C. & Swartz, D. A. in Evolution of Massive Stars: Confrontation Between Theory and Observation (eds Vanbeveren, D. et al.) 425−437 (Vrije Univ., Brussels, 1994).
14.	Bhattacharya, D. & van den Heuvel, E. P. J. Phys. Rep. 203, 1−124 (1991). | Article | ISI | ChemPort |
15.	Habets, G. M. H. J. Astr. Astrophys. 187, 209−230 (1986).
16.	Nomoto, K. & Hashimoto, M. Phys.Rep. 163, 13−36 (1988). | ChemPort |
17.	Van den Heuvel, E. P. J. in Interacting Binaries (eds Nussbaumer, H. & Orr, A.) 263−474 (Springer, Berlin, 1994).
18.	Pols, O. R., Coté, J., Waters, L. B. F. M. & Heise, J. Astr. Astrophys. 241, 419−438 (1991). | ChemPort |
19.	Van den Bergh, S. A. Rev. Astr. Astrophys. 29, 363−407 (1991). | Article |
20.	Muller, R. A. et al. Astrophys. J. 384, L9−L13 (1992). | Article |
21.	Swartz, D. A. & Wheeler, J. C. Astrophys. J. 379, L13−L16 (1991). | Article | ChemPort |
22.	de Vaucouleurs, G. Astrophys. J. 227, 729−755 (1979). | Article |
23.	Jeffery, D. J., Branch, D., Filippenko, A. V. & Nomoto, K. Astrophys. J. 377, L89−L92 (1991). | Article | ChemPort |
24.	Shigeyama, T. et al. Astrophys. J. 420, 341−347 (1994). | Article | ISI | ChemPort |
25.	Rupen, M. P. et al. IAU Circ. No. 5963 (1994).
26.	Yamaoka, H., Nomoto, K., Shigeyama, T. & Thielemann, F.-K. Astrophys. J. 393, L55−L58 (1992). | Article |
27.	Nomoto, K., Yamaoka, H., Shigeyama, T. & Iwamoto, K. in Supernovae and Supernova Remnants (eds McCray, R. & Wang, Z.) (IAU colloq. No. 145, Kluwer, Dordrecht, in the press).
28.	Panagia, N. in High Energy Phenomena Around Collapsed Stars (ed. Pacini, F.) 33−49 (Reidel, Dordrecht, 1987). | ChemPort |
29.	Leibundgut, B. et al. Astrophys. J. 371, L23−L26 (1990).
30.	Leibundgut, B. et al. Astr. J. 105, 301−313 (1993). | Article |