A `Hypernova' model for SN 1998bw associated with gamma-ray burst of 25 April 1998

K. Iwamoto; P. A. Mazzali; K. Nomoto; H. Umeda; T. Nakamura; F. Patat; I. J. Danziger; T. R. Young; T. Suzuki; T. Shigeyama; T. Augusteijn; V. Doublier; J. -F. Gonzalez; H. Boehnhardt; J. Brewer; O. R. Hainaut; C. Lidman; B. Leibundgut; E. Cappellaro; M. Turatto; T. J. Galama; P. M. Vreeswijk; C. Kouveliotou; J. van Paradijs; E. Pian; E. Palazzi; F. Frontera

doi:10.1038/27155

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arXiv · astro-ph/9806382

A `Hypernova' model for SN 1998bw associated with gamma-ray burst of 25 April 1998

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Abstract

The discovery of the peculiar supernova (SN) 1998bw and its possible association with the gamma-ray burst (GRB) 980425$^{1,2,3}$ provide new clues to the understanding of the explosion mechanism of very massive stars and to the origin of some classes of gamma-ray bursts. Its spectra indicate that SN~1998bw is a type Ic supernova$^{3,4}$, but its peak luminosity is unusually high compared with typical type Ic supernovae$^3$. Here we report our findings that the optical spectra and the light curve of SN 1998bw can be well reproduced by an extremely energetic explosion of a massive carbon+oxygen (C+O) star. The kinetic energy is as large as $\sim 2-5 \times 10^{52}$ ergs, more than ten times the previously known energy of supernovae. For this reason, the explosion may be called a `hypernova'. Such a C+O star is the stripped core of a very massive star that has lost its H and He envelopes. The extremely large energy, suggesting the existence of a new mechanism of massive star explosion, can cause a relativistic shock that may be linked to the gamma-ray burst.

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K. Iwamoto, P. A. Mazzali, K. Nomoto, H. Umeda, T. Nakamura, F. Patat, I. J. Danziger, T. R. Young, T. Suzuki, T. Shigeyama, T. Augusteijn, V. Doublier, J. -F. Gonzalez, H. Boehnhardt, J. Brewer, O. R. Hainaut, C. Lidman, B. Leibundgut, E. Cappellaro, M. Turatto, T. J. Galama, P. M. Vreeswijk, C. Kouveliotou, J. van Paradijs, E. Pian, E. Palazzi, F. Frontera. 1998-08-06. A `Hypernova' model for SN 1998bw associated with gamma-ray burst of 25 April 1998. https://doi.org/10.1038/27155

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