Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aipc..847..445n&link_type=abstract
ORIGIN OF MATTER AND EVOLUTION OF GALAXIES: International Symposium on Origin of Matter and Evolution of Galaxies 2005: New Hori
Astronomy and Astrophysics
Astrophysics
Stellar Structure, Interiors, Evolution, Nucleosynthesis, Ages, Supernovae, Black Holes, Abundances, Chemical Composition
Scientific paper
Two-dimensional hydrodynamic simulations are performed to investigate explosive nucleosynthesis in a collapsar using the model of MacFadyen and Woosley (1999). It is shown that 56Ni is not produced in the jet of the collapsar sufficiently to explain the observed amount of a hypernova when the duration of the explosion is ~10 sec, which is considered to be the typical timescale of explosion in the collapsar model. Even though considerable amount of 56Ni is synthesized if all explosion energy is deposited initially, the opening angles of the jets become too wide to realize highly relativistic outflows and gamma-ray bursts in such a case. Moreover, the synthesized 56Ni can not be used to brighten the supernova, since most of 56Ni exist in the jet component rather than in the supernova ejecta, and the jet becomes optically thin before considerable amount of 56Ni decays. From these results, it is concluded that the origin of 56Ni in hypernovae is not the explosive nucleosynthesis in the jet. We consider that the idea that the origin is the explosive nucleosynthesis in the accretion disk is more promising. We also show that the explosion becomes bi-polar naturally due to the effect of the deformed progenitor. This fact suggests that the 56Ni synthesized in the accretion disk and conveyed as outflows are blown along to the rotation axis, which will explain the line features of SN 1998bw and double peaked line features of SN 2003jd. This feature will help the idea of the accretion disk mentioned above. We predict that some fraction of 56Ni synthesized in the jet may show Lorentz boosted line profiles. That is, highly blue shifted (or red shifted) broad line features might be observed in the future. We show that abundance of nuclei whose mass number ~ 40 in the ejecta depends sensitively on the energy deposition rate, which is a result of active incomplete silicon burning and alpha-rich freezeout. So it may be determined by observations of chemical composition in metal poor stars which model is the proper one as a model of a gamma-ray burst accompanied by a hypernova.
Mizuta Akira
Nagataki Shigehiro
Sato Kachishige
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