EDP Sciences
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Volume 471, Number 1, August III 2007
Page(s) 227 - 236
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20066593

A&A 471, 227-236 (2007)
DOI: 10.1051/0004-6361:20066593

Nucleosynthesis in neutron-rich ejecta from quark-novae

P. Jaikumar1, B. S. Meyer2, K. Otsuki3, and R. Ouyed4

1  Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA
    e-mail: jaikumar@imsc.res.in
2  Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA
3  Department of Astronomy and Astrophysics, Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA
4  Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4, Canada

(Received 18 October 2006 / Accepted 23 May 2007)

We explore heavy-element nucleosynthesis by rapid neutron capture (r-process) in the decompressing ejecta from the surface of a neutron star. The decompression is triggered by a violent phase transition to strange quark matter (quark-nova scenario). The presence of neutron-rich large Z nuclei (40,95) < (Z,A) < (70,177), the large neutron-to-seed ratio, and the low electron fraction $Y_{\rm e}$ ~ 0.03 in the decompressing ejecta present favorable conditions for the r-process. We perform network calculations that are adapted to the quark-nova conditions, and which mimic usual $(n-\gamma)$ equilibrium r-process calculations during the initially cold decompression phase. They match to dynamical r-process calculations at densities below neutron drip (4 $\times$ 1011 g cm-3). We present results for the final element abundance distribution with and without heating from nuclear reactions, and compare to the solar abundance pattern of r-process elements. We highlight the distinguishing features of quark-novae by contrasting it with conventional nucleosynthetic sites such as type II supernovae and neutron star mergers, especially in the context of heavy-element compositions of extremely metal-deficient stars.

Key words: dense matter -- nuclear reactions, nucleosynthesis, abundances -- stars: neutron

© ESO 2007

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