Binary neutron star mergers: Dependence on the nuclear equation of state

By K. Hotokezaka, K. Kyutoku, Hirotada Okawa, M. Shibata, Kentaro Kiuchi. 2011

162 citations recorded by the source corpus.

We perform a numerical-relativity simulation for the merger of binary neutron stars with 6 nuclear-theory-based equations of states (EOSs) described by piecewise polytropes. Our purpose is to explore the dependence of the dynamical behavior of the binary neutron star merger and resulting gravitational waveforms on the EOS of the supernuclear-density matter. The numerical results show that the merger process and the first outcome are classified into three types: (i) a black hole is promptly formed, (ii) a short-lived hypermassive neutron star (HMNS) is formed, (iii) a long-lived HMNS is formed. The type of the merger depends strongly on the EOS and on the total mass of the binaries. For the EOS with which the maximum mass is larger than $2{M}_{\ensuremath{\bigodot}}$, the lifetime of the HMNS is longer than 10 ms for a total mass ${m}_{0}=2.7{M}_{\ensuremath{\bigodot}}$. A recent radio observation suggests that the maximum mass of spherical neutron stars is ${M}_{\mathrm{max}}\ensuremath{\ge}1.97\ifmmode\pm\else\textpm\fi{}0.04{M}_{\ensuremath{\bigodot}}$ in one $\ensuremath{\sigma}$ level. This fact and our results support the possible existence of a HMNS soon after the onset of the merger for a typical binary neutron star with ${m}_{0}=2.7{M}_{\ensuremath{\bigodot}}$. We also show that the torus mass surrounding the remnant black hole is correlated with the type of the merger process; the torus mass could be large, $\ensuremath{\ge}0.1{M}_{\ensuremath{\bigodot}}$, in the case that a long-lived HMNS is formed. We also show that gravitational waves carry information of the merger process, the remnant, and the torus mass surrounding a black hole.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/3ccad0223360ef0f7521cf095bec947cac4306fa

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Citations in the corpus

Origin of the heaviest elements: The rapid neutron-capture process (2019, background): “) and the EoS as it determines the value of Mc (Shibata et al., 2005; Shibata and Taniguchi, 2006; Kiuchi et al., 2009; Hotokezaka et al., 2011; Kastaun et al., 2016): For a soft EoS that results in rather compact initial neutron stars before the merger, the HMNS collapses to a black hole on timesca”
Binary Neutron Star Mergers: Mass Ejection, Electromagnetic Counterparts, and Nucleosynthesis (2018, background): “…or included GR effects, but compromised on the treatment of NS matter (Shibata & Uryu 2000; Shibata et al. 2003, 2005; Baiotti et al. 2008; Kiuchi et al. 2010; Rezzolla et al. 2010, 2011; Hotokezaka et al. 2011, 2013a, 2013b; Palenzuela et al. 2013; Ruiz et al. 2016; Dietrich et al. 2017a, 2017b).”
The Einstein Toolkit: a community computational infrastructure for relativistic astrophysics (2011, methodology): “Many of the successful techniques used to evolve BH–BH binaries have proven to be equally applicable to merging NS–NS [54, 56–74] and BH–NS [44, 74–90] binaries (for reviews, see also [91, 92]), allowing for further investigations into the former and the first full GR simulations of the latter.”
Optical and X-ray emission from stable millisecond magnetars formed from the merger of binary neutron stars (2013, unknown): “…process (e.g., Ruffert & Janka 1999; Uryū et al. 2000; Rosswog & Liebendörfer 2003; Oechslin & Janka 2006; Chawla et al. 2010; Rezzolla et al. 2010; Hotokezaka et al. 2011) show that initially the end product is a hypermassive NS, which is (at least temporarily) stable togravitational collapse…”
Neutron-star Radius Constraints from GW170817 and Future Detections (2017, background): “The threshold binary mass Mthres depends sensitively on the EoS (Shibata 2005; Baiotti et al. 2008; Hotokezaka et al. 2011; Bauswein et al. 2013a).”
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…”
Three-dimensional GRMHD Simulations of Neutrino-cooled Accretion Disks from Neutron Star Mergers (2017, background): “The initial torus mass we adopt is also fairly typical of NS mergers (e.g., Hotokezaka et al. 2011; Foucart et al. 2017).”
NEUTRINO-DRIVEN WINDS IN THE AFTERMATH OF A NEUTRON STAR MERGER: NUCLEOSYNTHESIS AND ELECTROMAGNETIC TRANSIENTS (2015, background): “For example, recent studies in full GR (Hotokezaka et al. 2011, 2013; Sekiguchi et al. 2015) and in the conformal flatness approximation (Bauswein et al. 2013) agree that shocks are more important for the dynamic ejecta in the GR case, especially when a soft equation of state is used.”
Constraining the Maximum Mass of Neutron Stars from Multi-messenger Observations of GW170817 (2017, background): “…merger product undergoes “prompt” dynamical-timescale collapse to a black hole (BH) (e.g. Shibata 2005; Shibata & Taniguchi 2006; Baiotti et al. 2008; Hotokezaka et al. 2011), where the proportionality factor k ≈ 1.3 − 1.6 is greater for smaller values of the NS “compactness”, Cmax =…”
Delayed outflows from black hole accretion tori following neutron star binary coalescence (2013, background): “…from a NS-NS merger, following a metastable hypermassive NS phase, is typically surrounded by a thick torus of mass ∼ 10−3 − 0.1M⊙ (Ruffert & Janka 1999; Uryū et al. 2000; Rosswog & Liebendörfer 2003; Oechslin & Janka 2006; Chawla et al. 2010; Rezzolla et al. 2010; Hotokezaka et al. 2011).”
Cosmological Fast Radio Bursts from Binary Neutron Star Mergers (2013, methodology): “This picture is consistent with the latest numerical simulations of NS-N mergers, but a fraction of merger events may form a HMNS that survives for a time scale longer than milliseconds before c llapsing into a black hole (Hotokezaka et al. 2011; Faber & Rasio 2012).”