Schedule Mar 23, 2007
Nucleosynthesis in Jet-induced Supernovae
Nozomu Tominaga (Univ. Tokyo)

Long-duration gamma-ray bursts (GRBs) are thought to be connected with luminous and energetic supernovae [SNe, called hypernovae (HNe)] resulting from the black-hole (BH) forming collapse of massive stars. For recent nearby GRBs~060505 and 060614, however, the expected SNe have not been detected. The upper limits to the SN brightness are about 100 times fainter than GRB-associated HNe (GRB-HNe), corresponding to the upper limits to the ejected 56Ni masses of M(56Ni)~10^{-3} Msun. SNe with a small amount of 56Ni ejection are observed as faint Type II SNe. HNe and faint SNe are thought to be responsible for the formation of extremely metal-poor (EMP) stars. In this paper, a relativistic jet-induced BH forming explosion of the 40 Msun star is investigated and hydrodynamic and nucleosynthetic models are presented. These models can explain both GRB-HNe and GRBs without bright SNe in a unified manner. Their connection to EMP stars is also discussed. We suggest that GRBs without bright SNe are likely to synthesize M(56Ni)~10^{-4}-10^{-3} Msun or ~10^{-6} Msun.

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