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

Iwamoto, K.; Mazzali, P.A.; Nomoto, K.; Umeda, H.; Nakamura, T.; Patat, F.; Danziger, I.J.; Young, T.R.; Suzuki, T.; Shigeyama, T.

doi:10.1038/27155

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

Jun, 1998

8 pages

Published in:

Nature 395 (1998) 672-674

e-Print:

astro-ph/9806382 [astro-ph]

DOI:

10.1038/27155

Report number:

ESO-1292

View in:

ADS Abstract Service

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Abstract: (arXiv)

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.