A hypernova model for the supernova associated with the γ-ray burst of 25 April 1998

• Published in: Nature (London) Vol. 395; no. 6703; pp. 672 - 674
• Main Authors: Nomoto, K, Iwamoto, K, Mazzali, P. A, Umeda, H, Nakamura, T, Patat, F, Danziger, I. J, Young, T. R, Suzuki, T, Shigeyama, T, Augusteijn, T, Doublier, V, Gonzalez, J.-F, Boehnhardt, H, Brewer, J, Hainaut, O. R, Lidman, C, Leibundgut, B, Cappellaro, E, Turatto, M, Galama, T. J, Vreeswijk, P. M, Kouveliotou, C, van Paradijs, J, Pian, E, Palazzi, E, Frontera, F
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 15-10-1998; Nature Publishing Group
• Subjects: Astronomy; Astrophysics; Earth, ocean, space; Exact sciences and technology; Gamma rays; Gamma-ray sources ; gamma-ray bursts; Late stages of stellar evolution (including black holes); Physics; Solar and Stellar Astrophysics; Stars; Stellar systems. Galactic and extragalactic objects and systems. The universe; Supernovae; Unidentified sources and radiation outside the solar system; Type I supernova; Supernovae explosion; Relativistic shock wave; Supernovae; Light curves; Cosmic gamma bursts; Optical spectrum; Massive stars
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/27155

The discovery of the unusual supernova SN1998bw, and its possible association with the γ-ray burst GRB 980425, provide new insights into the explosion mechanism of very massive stars and the origin of some classes of γ-ray bursts. Optical spectra indicate that SN1998bw is a type Ic supernova,, but its peak luminosity is unusually high compared with typical type Ic supernovae. Here we report our findings that the optical spectra and the light curve of SN1998bw can be well reproduced by an extremely energetic explosion of a massive star composed mainly of carbon and oxygen (having lost its hydrogen and helium envelopes). The kinetic energy of the ejecta is as large as +(2-5)× 1052 erg, more than ten times that of previously observed supernovae. This type of supernova could therefore be termed 'hypernova'. The extremely large energy suggests the existence of a new mechanism of massive star explosion that can also produce the relativistic shocks necessary to generate the observed γ-rays.