SYSTEMATICS OF DYNAMICAL MASS EJECTION, NUCLEOSYNTHESIS, AND RADIOACTIVELY POWERED ELECTROMAGNETIC SIGNALS FROM NEUTRON-STAR MERGERS

By A. Bauswein, S. Goriely, H. J. M. Astrophysics, Garching, Universit́e Libre de Bruxelles. 2013

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We investigate systematically the dynamical mass ejection, r-process nucleosynthesis, and properties of electromagnetic counterparts of neutron-star (NS) mergers in dependence on the uncertain properties of the nuclear equation of state (EOS) by employing 40 representative, microphysical high-density EOSs in relativistic, hydrodynamical simulations. The crucial parameter determining the ejecta mass is the radius R1.35 of a 1.35 M☉ NS. NSs with smaller R1.35 (“soft” EOS) eject systematically higher masses. These range from ∼10−3 M☉ to ∼10−2 M☉ for 1.35–1.35 M☉ binaries and from ∼5 × 10−3 M☉ to ∼2 × 10−2 M☉ for 1.2–1.5 M☉ systems (with kinetic energies between ∼5 × 1049 erg and 1051 erg). Correspondingly, the bolometric peak luminosities of the optical transients of symmetric (asymmetric) mergers vary between 3 × 1041 erg s−1 and 14 × 1041 erg s−1 (9 × 1041 erg s−1 and 14.5 × 1041 erg s−1) on timescales between ∼2 hr and ∼12 hr. If these signals with absolute bolometric magnitudes from −15.0 to −16.7 are measured, the tight correlation of their properties with those of the merging NSs might provide valuable constraints on the high-density EOS. The r-process nucleosynthesis exhibits a remarkable robustness independent of the EOS, producing a nearly solar abundance pattern above mass number 130. By the r-process content of the Galaxy and the average production per event the Galactic merger rate is limited to 4 × 10−5 yr−1 (4 × 10−4 yr−1) for a soft (stiff) NS EOS, if NS mergers are the main source of heavy r-nuclei. The production ratio of radioactive 232Th to 238U attains a stable value of 1.64–1.67, which does not exclude NS mergers as potential sources of heavy r-material in the most metal-poor stars.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/65ce23760a51c14b654937ae540a5e6ffc966e1c

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Citations in the corpus

GW170817: Joint Constraint on the Neutron Star Equation of State from Multimessenger Observations (2017, methodology): “…this observation with empirical relations between NS radii and the threshold mass for prompt collapse, which was previously found by means of simulations with an approximate treatment of general relativity (GR; Bauswein et al. 2013a), to tentatively rule out EOSs predicting very small NS radii.”
Long-term GRMHD simulations of neutron star merger accretion discs: implications for electromagnetic counterparts (2018, background): “The former is launched on the dynamical time of the merger (∼ms) by tidal forces and hydrodynamic interactions (e.g., Bauswein et al. 2013; Hotokezaka et al. 2013).”
The cocoon emission - an electromagnetic counterpart to gravitational waves from neutron star mergers (2017, background): “Numerical simulations (e.g. Rosswog et al. 1998; Hotokezaka et al. 2011; Fernández & Metzger 2013; Hotokezaka et al. 2013b; Bauswein et al. 2013; Rosswog 2013; Perego et al. 2014a; Siegel et al. 2014; Wanajo et al. 2014; Just et al. 2015) suggest that the mergers are accompanied by significant mass…”
Europium production: neutron star mergers versus core-collapse supernovae (2013, background): “Rosswog et al. (1999, 2000) and more recently Oechslin et al. (2007), Bauswein et al. (2013), Rosswog (2013), Hotokeza a et al. (2013), Kyutoku et al. (2013) showed that up to 10−2 M⊙ of r-process matter may be ejected in a single coalescence event.”
The long-term evolution of neutron star merger remnants – I. The impact of r-process nucleosynthesis (2013, background): “For nsns mergers we found a range from 8× 10−3 - 4× 10−2 M (Rosswog 2013), approximate GR calculations find 10−3 − 2× 10−2 M (Bauswein et al. 2013) and full GR calculations (Hotokezaka et al. 2013) find 10−4 − 10−2 M .”
AT 2017gfo: An Anisotropic and Three-component Kilonova Counterpart of GW170817 (2017, background): “In our analysis, we did not consider the possible presence of a small amount (∼ 10−4 M ) of free-neutron ejecta (Bauswein et al. 2013), which could contribute to the UV/visible emission a few hours after the merger (Metzger et al. 2015).”
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”
Neutron-powered precursors of kilonovae (2014, methodology): “The other merger simulations presented in Bauswein et al. (2013) show similar populations of rapidly expanding SPH particles, based on the same expansion timescale criterionτexp ∼< 5 ms found to result in free neutrons in the case described above.”
r-PROCESS LANTHANIDE PRODUCTION AND HEATING RATES IN KILONOVAE (2015, background): “…the material was ejected tidally (Lattimer et al. 1977; Freiburghaus et al. 1999), dynamically from the region where the two neutron stars collide (Bauswein et al. 2013; Hotokezaka et al. 2013a), or from the accretion disk that forms after the merger (Fernández & Metzger 2013; Perego et al.…”
Delayed outflows from black hole accretion tori following neutron star binary coalescence (2013, background): “…& Schramm 1974; Rosswog et al. 1999; Rosswog 2005; Chawla et al. 2010; Stephens et al. 2011; East et al. 2012; Rosswog 2012; Rosswog et al. 2013; Bauswein et al. 2013), and recent nuclear reaction network calculations largely agree on the amount of radioactive heating provided by such decaying…”
Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers (2017, background): “However, this optical kilonova component may be obscured by lanthanides and actinides that were synthesized in the more neutron-rich dynamical ejecta, particularly because this ejecta component is quasispherical in NSNS mergers (e.g., Bauswein et al. 2013).”
PRODUCTION OF ALL THE r-PROCESS NUCLIDES IN THE DYNAMICAL EJECTA OF NEUTRON STAR MERGERS (2014, background): “The behavior of mass ejection described here is in qualitative agreement with the previous full GR (Hotokezaka et al. 2013a, for soft EOSs) and approximate GR (Bauswein et al. 2013, for the same SFHo EOS) works.”
Neutron-star Radius Constraints from GW170817 and Future Detections (2017, methodology): “The threshold binary mass Mthres depends sensitively on the EoS (Shibata 2005; Baiotti et al. 2008; Hotokezaka et al. 2011; Bauswein et al. 2013a).”
Comprehensive nucleosynthesis analysis for ejecta of compact binary mergers (2014, methodology): “MNRAS 448, 541–567 (2015) at M PI A strophysics on M ay 8, 2015 http://m nras.oxfordjournals.org/ D ow nloaded from mergers (e.g. Bauswein et al. 2013b), for example, tend to produce faster ejecta than Newtonian simulations (e.g. Roberts et al. 2011; Korobkin et al. 2012; Grossman et al. 2014;…”
Mass Ejection from the Remnant of a Binary Neutron Star Merger: Viscous-radiation Hydrodynamics Study (2017, background): “…to be ejected from the system with high velocity (10%–30% of the speed of light) during the merger and post-merger phases(e.g., Dessart et al. 2009; Bauswein et al. 2013; Fernández & Metzger 2013; Hotokezaka et al. 2013b; Rosswog 2013; Metzger & Fernández 2014; Perego et al. 2014; Foucart et al.…”
The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South (2017, background): “The red component most likely represents material in the equatorial plane, which could originate in tidal tails of the disrupted neutron star, spiral mode instabilities, or winds from an accretion disk (e.g., Rosswog et al. 1999; Bauswein et al. 2013; Siegel & Metzger 2017).”
BRIGHT “MERGER-NOVA” FROM THE REMNANT OF A NEUTRON STAR BINARY MERGER: A SIGNATURE OF A NEWLY BORN, MASSIVE, MILLISECOND MAGNETAR (2013, background): “Numerical simulations show that a more isotropic, sub-relativistic (vej ∼ 0.15−0.25c) outflow could be ejected during a merger, which could include the tidal tail matter during the merger and the matter from the accretion disk (e.g. Rezzolla et al. 2011; Bauswein et al. 2013; Rosswog et al. 2013).”