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First Stars III
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Poster
Title: Study of the 12N(p,gamma)13O reaction in relation to Population III star evolution Author(s): Adriana Banu Abstract:The reaction rate for the radiative proton capture on the drip line nucleus 12N is studied at the Cyclotron Institute/Texas A&M University using an indirect method. This reaction is important in the hot pp chain nuclear burning in hydrogen-rich massive objects [1]. In 1986, Fuller, Woosley, and Weaver [2] addressed the classic problem of supermassive star evolution - given that a nonrotating supermassive star has formed and contracted to its instability point, does the rapid nuclear burning in the subsequent collapse generate enough thermal energy to stabilize the collapse and trigger an explosion? It was found that Population III stars with M>5*105 solar masses and Z <<0.005 will collapse to black holes while stars of higher metallicity will explode. For the failed explosions, it is reasoned that in the short time scales of the collapse insufficient amounts of 12C and other heavier isotopes are produced by the 3alpha process but alternative paths from the slow 3alpha process to produce CNO seed nuclei could change their fate. In 1989, M. Wiescher et al [1] reinvestigated the reaction rates for nuclei up to oxygen and suggested several reaction sequences (hot pp chains) that would permit very massive stars with low-metallicity to bypass the 3alpha process. The 12N(p,gamma)13O reaction is an important branch point in one of such alternative paths. Primary beam from the K500 superconductive cyclotron is used to produce in-flight radioactive 12N beam separated with recoil spectrometer MARS [3]. We used the 14N(12N,13O)13C proton transfer reaction to extract the asymptotic normalization coefficient (ANC) for the virtual decay 13O->12N+p, and calculate from it the direct component of the astrophysical S-factor. We evaluated the impact of this measurement on the reaction rate of 12N(p,gamma)13O for nucleosynthesis in Pop III stars with low metallicity. Results of this study are presented.
[1] M. Wiescher et al., The Astrophysical Journal, 343: 352-364, 1989.
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