Accurate evolutions of unequal-mass neutron-star binaries: properties of the torus and short GRB engines

By Luciano Rezzolla, Luca Baiotti, B. Giacomazzo, David Link, J. Font. 2010

158 citations recorded by the source corpus.

We present new results from accurate and fully general-relativistic simulations of the coalescence of unmagnetized binary neutron stars with various mass ratios. The evolution of the stars is followed through the inspiral phase, the merger, and the prompt collapse to a black hole, up until the appearance of a thick accretion disc, which is studied as it enters and remains in a regime of quasi-steady accretion. Although a simple ideal-fluid equation of state with Γ = 2 is used, this work presents a systematic study within a fully general-relativistic framework of the properties of the resulting black-hole–torus system produced by the merger of unequal-mass binaries. More specifically, we show that (1) the mass of the torus increases considerably with the mass asymmetry, and equal-mass binaries do not produce significant tori if they have a total baryonic mass Mtot ≳ 3.7 M⊙; (2) tori with masses Mtor ∼ 0.2 M⊙ are measured for binaries with Mtot ∼ 3.4 M⊙ and mass ratios q ∼ 0.75–0.85; (3) the mass of the torus can be estimated by the simple expression , involving the maximum mass for the binaries and coefficients constrained from the simulations, and suggesting that the tori can have masses as large as for Mtot ∼ 2.8 M⊙ and q ∼ 0.75–0.85; (4) using a novel technique to analyze the evolution of the tori, we find no evidence for the onset of non-axisymmetric instabilities and that very little, if any, of their mass is unbound; (5) finally, for all the binaries considered, we compute the complete gravitational waveforms and the recoils imparted to the black holes, discussing the prospects of the detection of these sources for a number of present and future detectors.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/ef0a4eb5a8f4d6765a2f0ac8157e6b2989dad125

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In Astronomy and Astrophysics

1. B. Metzger
2. Bing Zhang
3. David Radice
4. E. Berger
5. Albino Perego
6. R. Fern'andez
7. Luke F. Roberts
8. D. Kasen

Citations in the corpus

• The electromagnetic signals of compact binary mergers (2012, background): “…energetic subrelativistic and mildly relativistic outflows (e.g. Rosswog et al. 1999; Ruffert & Janka 2001; Rosswog 2005; Rosswog & Price 2007; Yamamoto, Shibata & Taniguchi 2008; Rezzolla et al. 2010), unless the equation of state at supranuclear densities is extremely soft (Rosswog et al. 2000).”
• Delayed outflows from black hole accretion tori following neutron star binary coalescence (2013, background): “a ∼ 0.7− 0.8 (e.g., Rezzolla et al. 2010) 2 The formation of heavy nuclei would indeed occur at radii within our simulation grid, however, see §5.1 in all variables.”
• A POSSIBLE CONNECTION BETWEEN FAST RADIO BURSTS AND GAMMA-RAY BURSTS (2013, background): “However, any FRB emission would still be absorbed by the ejecta launched during the merger process, which has a mass at least 10−4M⊙ (e.g. Freiburghaus et al. 1999; Rezzolla et al. 2010; Hotokezaka et al. 2013).”
• FORMATION OF STABLE MAGNETARS FROM BINARY NEUTRON STAR MERGERS (2013, background): “Simulations of unstable HMNSs, on the other hand, show a clear increase in the rest-mass density (see, e.g., the left panel of Figure A1 in Rezzolla et al. 2010).”
• 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 MISSING LINK: MERGING NEUTRON STARS NATURALLY PRODUCE JET-LIKE STRUCTURES AND CAN POWER SHORT GAMMA-RAY BURSTS (2011, background): “…up to black-hole (BH) formation, without and with magnetic fields (Shibata & Taniguchi 2006; Baiotti et al. 2008; Anderson et al. 2008; Liu et al. 2008; Giacomazzo et al. 2009, 2011), and with idealized or realistic equations-of-state (EOS; Rezzolla et al. 2010; Kiuchi et al. 2010).”
• Three-dimensional GRMHD Simulations of Neutrino-cooled Accretion Disks from Neutron Star Mergers (2017, background): “The BH spins resulting from NS–NS mergers leading to prompt BH formation are typically χBH ≈ 0.8 (Kiuchi et al. 2009; Rezzolla et al. 2010; Bernuzzi et al. 2014) and cannot be significantly larger (Kastaun et al. 2013); the case of delayed BH formation is typically not much smaller, χBH .”
• Gravitational waves and non-axisymmetric oscillation modes in mergers of compact object binaries (2011, background): “With less numerical damping, the gravitational wave amplitude could remain strong for a much longer time, leading to an enhanced signal (for a recent long-term evolution see Rezzolla et al. (2010)).”
• Kilonova light curves from the disc wind outflows of compact object mergers (2014, background): “It is more likely, however, that the BH remnant of a compact object merger is a rapidly rotating (Oechslin, Janka & Marek 2007; Kiuchi et al. 2009; Rezzolla et al. 2010).”
• Dynamical Mass Ejection from Binary Neutron Star Mergers (2016, background): “Mass ejection may change quantitatively and possibly qualitatively with different EOS and with unequal mass binaries (Rezzolla et al. 2010; Hotokezaka et al. 2013; Bauswein et al. 2013; Sekiguchi et al. 2015; Dietrich et al. 2015; Palenzuela et al. 2015; Foucart et al. 2016), or with the inclusion…”
• Optical and X-ray emission from stable millisecond magnetars formed from the merger of binary neutron stars (2013, background): “…of the merger 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…”
• PULSAR J0453+1559: A DOUBLE NEUTRON STAR SYSTEM WITH A LARGE MASS ASYMMETRY (2015, methodology): “According to recent simulations (Rezzolla et al. 2010; Hotokezaka et al. 2013 and Rosswog 2013), such mergers result in a much larger release of heavy r-process elements into space (Just et al. 2015), possibly explaining the heavy element abundances in our Galaxy.”
• Black hole and neutron star mergers in galactic nuclei (2018, background): “…intensity of the gammaray radiation, which primarily depends on the amount of mass available for accretion, is primarily determined by the properties (namely mass and equation of state) of the merging stars (Shibata et al. 2006; Rezzolla et al. 2010; Giacomazzo et al. 2013; Hotokezaka et al. 2013).”
• The physics of gamma-ray bursts & relativistic jets (2014, background): “…1998; Kulkarni, 2005; Metzger et al., 2010), and a long-lasting radio afterglow due to the interaction of the ejecta with the surrounding matter (Rezzolla et al., 2010; Nakar and Piran, 2011; Shibata et al., 2011; Metzger and Berger, 2012; Piran et al., 2013; Kyutoku et al., 2012, 2013).”