On the astrophysical robustness of the neutron star merger r-process

By Oleg Korobkin, Stephan Rosswog, A. Arcones, C. Winteler. 2012

476 citations recorded by the source corpus.

In this study we explore nucleosynthesis in the dynamic ejecta of compact binary mergers. We are particularly interested in the question how sensitive the resulting abundance patterns are to the parameters of the merging system. Therefore, we systematically investigate combinations of neutron star masses in the range from 1.0 to 2.0 M? and, for completeness, we compare the results with those from two simulations of a neutron star black hole merger. The ejecta masses vary by a factor of 5 for the studied systems, but all amounts are (within the uncertainties of the merger rates) compatible with being a major source of the cosmic r-process. The ejecta undergo robust r-process nucleosynthesis which produces all the elements from the second to the third peak in close-to-solar ratios. Most strikingly, this r-process is extremely robust, and all 23 investigated binary systems yield practically identical abundance patterns. This is mainly the result of the ejecta being extremely neutron rich (Ye similar to 0.04) and the r-process path meandering along the neutron drip line so that the abundances are determined entirely by nuclear rather than astrophysical properties. While further questions related to galactic chemical evolution need to be explored in future studies, we consider this robustness together with the ease with which both the second and third peak are reproduced as strong indications that compact binary mergers are prime candidates for the sources of the observed unique heavy r-process component.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/18ad76e3ab5419ec6001a40cf83bef2a786100d1

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Citations in the corpus

Production of the entire range of r-process nuclides by black hole accretion disc outflows from neutron star mergers (2016, background): “…unbound matter to be highly neutron-rich, with an electron fraction Ye ∼< 0.1, sufficiently low to produce a robust abundance pattern for heavy nuclei with A ∼> 130 as the result of fission cycling (e.g., Goriely et al. 2011, Korobkin et al. 2012, Bauswein et al. 2013, Mendoza-Temis et al. 2015).”
PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS (2014, background): “Similar results were obtained from the Newtonian simulations of NS–NS and BH–NS mergers by Roberts et al. (2011), Korobkin et al. (2012), Rosswog et al. (2014).”
Binary Neutron Star Mergers: Mass Ejection, Electromagnetic Counterparts, and Nucleosynthesis (2018, background): “…that are thought to be a likely site for the production of r-process nuclei (Lattimer & Schramm 1974; Symbalisty & Schramm 1982; Eichler et al. 1989; Meyer 1989; Freiburghaus et al. 1999; Goriely et al. 2011; Korobkin et al. 2012; Wanajo et al. 2014; Just et al. 2015; Thielemann et al. 2017).”
The multimessenger picture of compact object encounters: binary mergers versus dynamical collisions (2012, background): “Our recent study (Korobkin et al. 2012) finds indeed that the dynamic ejecta of ns2 and nsbh mergers are excellent candidates for the production sites of the robust heavy r-process patter with A larger than ∼120.”
The Combined Ultraviolet, Optical, and Near-infrared Light Curves of the Kilonova Associated with the Binary Neutron Star Merger GW170817: Unified Data Set, Analytic Models, and Physical Implications (2017, unknown): “The temporal evolution of the radioactive heating rate can be approximated by the parameterized form (Korobkin et al. 2012): p s = ´ ´ - -- -⎜ ⎟ ⎡ ⎣⎢ ⎛ ⎝ ⎞ ⎠ ⎤ ⎦⎥ ( ) ( ) L t M t t 4 10 0.5 arctan erg s , 1 in 18 rp 1 0 1.3 1 where Mrp is the mass of the r-process ejecta, and =t 1.3 s0 and s = 0.11…”
THE r-PROCESS NUCLEOSYNTHESIS IN THE VARIOUS JET-LIKE EXPLOSIONS OF MAGNETOROTATIONAL CORE-COLLAPSE SUPERNOVAE (2015, background): “More sophisticated investigations (e.g., Goriely et al. 2011; Korobkin et al. 2012; Bauswein et al. 2013), have shown that the ejecta remain extremely neutron-rich, producing heavier nuclei than the second r-process peak due to strong neutron capture with fission re-cycling.”
The cocoon emission - an electromagnetic counterpart to gravitational waves from neutron star mergers (2017, unknown): “The first, ε̇ = ε̇0, where ε̇0 = 1010 erg gr−1 s−1 (Freiburghaus et al. 1999; Metzger et al. 2010; Korobkin et al. 2012; Hotokezaka et al. 2017), which is typical for dynamic ejecta that is dominated by elements with mass number A> 130.”
Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817 (2017, methodology): “In the ejected material, rapid neutron capture nucleosynthesis (r-process) takes place (e.g., Lattimer & Schramm 1974; Eichler et al. 1989; Korobkin et al. 2012; Wanajo et al. 2014).”
Impact of ejecta morphology and composition on the electromagnetic signatures of neutron star mergers (2017, background): “They fall in two categories, "tidal ejecta" unbound by gravitational torques and "interaction ejecta" that become unbound due to hydrodynamic processes (see Fig.2 in Korobkin et al. (2012)).”
Colloquium : Superheavy elements: Oganesson and beyond (2019, background): “Numerical simulations show that high neutron densities can be achieved in the dynamical ejecta of this astrophysical scenario (Bauswein et al., 2013; Goriely et al., 2011; Kasen et al., 2017; Korobkin et al., 2012; Radice et al., 2016; Rosswog et al., 1999; Sekiguchi et al., 2015) and in the accreti”
NUGRID STELLAR DATA SET. I. STELLAR YIELDS FROM H TO BI FOR STARS WITH METALLICITIES Z = 0.02 and Z = 0.01 (2013, background): “For a review of the different scenarios and recent r-process results see Thielemann et al. (2011); Winteler et al. (2012) and Korobkin et al. (2012).”
Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers (2017, background): “…of fission cycles (e.g., Goriely et al. 2005), with little sensitivity to binary parameters or the equation of state (e.g., Goriely et al. 2011; Korobkin et al. 2012; Bauswein et al. 2013), depending instead on nuclear physics properties such as the fission fragment distribution (e.g., Eichler…”
The Origin of r-process Elements in the Milky Way (2017, background): “To agree with observations, a feasible candidate needs to be able to reproduce the observed pattern robustly, with little sensitivity to the variations in system parameters (Korobkin et al. 2012).”
BRIGHT “MERGER-NOVA” FROM THE REMNANT OF A NEUTRON STAR BINARY MERGER: A SIGNATURE OF A NEWLY BORN, MASSIVE, MILLISECOND MAGNETAR (2013, unknown): “…by (e.g. Kasen & Bildsten 2010) dE′int dt′ = ξL′sd + L ′ ra − L′e − P ′ dV ′ dt′ , (3) where the comoving luminosities read L′sd = Lsd/D2, L′e = Le/D2, and L′ra= Lra D2 =4× 1049Mej,−2 [ 1 2 − 1 π arctan ( t′ − t′0 t′σ )]1.3 erg s−1(4) with t′0 ∼ 1.3 s and t′σ ∼ 0.11 s (Korobkin et al. 2012).”
r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE (2015, methodology): “This is the case for the tidal ejecta, which is predicted to have a very low electron fraction (Korobkin et al. 2012).”