The r-process in black hole-neutron star mergers based on a fully general-relativistic simulation

Nishimura, N.; Wanajo, Shinya; Sekiguchi, Y.; Kiuchi, Kenta; Kyutoku, Koutarou; Shibata, Masaru

doi:10.1088/1742-6596/665/1/012059

Cited by 9 publications

(11 citation statements)

References 16 publications

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“…One major exception is the UFD Reticulum II, in which most stars have highly super-solar [n/Fe] ratios (Ji et al 2016a,c). One explanation for this neutron-capture enhancement is that Reticulum II experienced a rare event, such as a merger between two neutron stars or a neutron star and a black hole, that produced a great deal of r-process material (Freiburghaus et al 1999;Nishimura et al 2016). Star 40 in Tri II has not been affected by such an event.…”

Section: Detailed Abundances Of One Starmentioning

confidence: 99%

Triangulum II. Not Especially Dense After All*

Kirby

Cohen

Simon

et al. 2017

ApJ

115

126

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Among the Milky Way satellites discovered in the past three years, TriangulumII has presented the most difficulty in revealing its dynamical status. Kirby et al. identified it as the most dark-matter-dominated galaxy known, with a mass-to-light ratio within the half-light radius of M L 3600 2100On the other hand, Martin et al. measured an outer velocity dispersion that is 3.5±2.1 times larger than the central velocity dispersion, suggesting that the system might not be in equilibrium. From new multi-epoch Keck/DEIMOS measurements of 13 member stars in TriangulumII, we constrain the velocity dispersion to be 3.4. Our previous measurement of v s , based on six stars, was inflated by the presence of a binary star with variable radial velocity. We find no evidence that the velocity dispersion increases with radius. The stars display a wide range of metallicities, indicating that TriangulumII retained supernova ejecta and therefore possesses, or once possessed, a massive dark matter halo. However, the detection of a metallicity dispersion hinges on the membership of the two most metalrich stars. The stellar mass is lower than galaxies of similar mean stellar metallicity, which might indicate that TriangulumII is either a star cluster or a tidally stripped dwarf galaxy. Detailed abundances of one star show heavily depressed neutron-capture abundances, similar to stars in most other ultra-faint dwarf galaxies but unlike stars in globular clusters.

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Section: Detailed Abundances Of One Starmentioning

confidence: 99%

Triangulum II. Not Especially Dense After All*

Kirby

Cohen

Simon

et al. 2017

ApJ

115

126

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“…Recent studies (Goriely et al 2011;Korobkin et al 2012;Goriely et al 2013;Wanajo, et al 2014;Nishimura et al 2016) have indicated that the r process in NSMs produces a final abundance pattern that can be similar to the solar r-process abundances, but only for heavier A>130 nuclei. However, it is possible (Shibagaki et al 2016) that the main effects of fission recycling may be to fill in the bypassed abundances in the main r-process as discussed below.…”

Section: Neutron Star Mergersmentioning

confidence: 99%

Impact of new data for neutron-rich heavy nuclei on theoretical models forr-process nucleosynthesis

Kajino

Mathews

2017

Rep. Prog. Phys.

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Current models for the r process are summarized with an emphasis on the key constraints from both nuclear physics measurements and astronomical observations. In particular, we analyze the importance of nuclear physics input such as beta-decay rates; nuclear masses; neutron-capture cross sections; beta-delayed neutron emission; probability of spontaneous fission, beta-and neutron-induced fission, fission fragment mass distributions; neutrino-induced reaction cross sections, etc. We highlight the effects on models for r-process nucleosynthesis of newly measured β-decay half-lives, masses, and spectroscopy of neutron-rich nuclei near the r-process path. We overview r-process nucleosynthesis in the neutrino driven wind above the proto-neutron star in core collapse supernovae along with the possibility of magneto-hydrodynamic jets from rotating supernova explosion models. We also consider the possibility of neutron star mergers as an r-process environment. A key outcome of newly measured nuclear properties far from stability is the degree of shell quenching for neutron rich isotopes near the closed neutron shells. This leads to important constraints on the sites for r-process nucleosynthesis in which freezeout occurs on a rapid timescale.

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“…Recent studies [29][30][31][32]35] have indicated that the r process in NSMs produces a final abundance pattern that can be similar to the solar r-process abundances, but only for heavier A>130 nuclei.…”

Section: Current Models For the R-processmentioning

confidence: 99%

“…[28][29][30][31][32][33][34][35]). The ejected matter from NSMs is very neutron-rich (⟨Z/A⟩ ≡ Y e ∼ 0.1).…”

Section: Current Models For the R-processmentioning

confidence: 99%

Origin of r-Process Elements and Galactic Chemodynamical Evolution

Mathews¹,

Shibagaki²,

Kajino³

2017

Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016)

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It has been known for more than half a century that about half of the elements heavier than iron are produced via rapid neutron capture in the r-process. Indeed, the basic physical conditions for the r-process are well constrained by simple nuclear physics. In spite of this simplicity, however, the unambiguous identification of the site for the r-process nucleosynthesis has remained elusive. Parametrically, one can divide current models for the r-process into three scenarios roughly characterized by the number of neutron captures per seed nucleus (n/s). This parameter, in turn is the consequence of a variety of conditions such as time-scale, baryon density, average charge per baryon, and entropy. Here, we summarize various proposed sites for the r-process along with their short comings. Insights from a variety of nuclear physics measurements, astronomical observations, and models for galactic chemo-dynamical evolution are summarized. A paradigm is proposed whereby one may be able to quantify the relative contributions of each astrophysical site.

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The r-process in black hole-neutron star mergers based on a fully general-relativistic simulation

Cited by 9 publications

References 16 publications

Triangulum II. Not Especially Dense After All*

Triangulum II. Not Especially Dense After All*

Impact of new data for neutron-rich heavy nuclei on theoretical models forr-process nucleosynthesis

Origin of r-Process Elements and Galactic Chemodynamical Evolution

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