Long-lived neutron-star remnants from asymmetric binary neutron star mergers: element formation, kilonova signals and gravitational waves

Abstract

We present 3D general-relativistic neutrino-radiation hydrodynamics simulations of two asymmetric binary neutron star mergers producing long-lived neutron stars remnants and spanning a fraction of their cooling time scale. The mergers are characterized by significant tidal disruption with neutron rich material forming a massive disc around the remnant. The latter develops one-armed dynamics that is imprinted in the emitted kilo-Hertz gravitational waves. Angular momentum transport to the disc is initially driven by spiral-density waves and enhanced by turbulent viscosity and neutrino heating on longer timescales. The mass outflows are composed by neutron-rich dynamical ejecta of mass $\sim 10^{-3}-10^{-2}{M}_{\odot }$ followed by a persistent spiral-wave/neutrino-driven wind of $\gtrsim 10^{-2}{M}_{\odot }$ with material spanning a wide range of electron fractions, $\sim 0.1-0.55$. Dynamical ejecta (winds) have fast velocity tails up to $\sim 0.8$ ($\sim 0.4$) c. The outflows are further evolved to days timescale using 2D ray-by-ray radiation-hydrodynamics simulations that include an online nuclear network. We find complete $r$-process yields and identify the production of ${}^{56}$Ni and the subsequent decay chain to ${}^{56}$Co and ${}^{56}$Fe. Synthetic kilonova light curves predict an extended (near-) infrared peak a few days postmerger originating from $r$-process in the neutron-rich/high-opacity ejecta and UV/optical peaks at a few hours (ten minutes) postmerger originating from weak $r$-process (free-neutron decay) in the faster ejecta components. Additionally, the fast tail of tidal origin generates kilonova afterglows potentially detectable in radio and X band on a few to ten years time scale. Quantitative effects originating from the tidal disruption merger dynamics are reflected in the multimessenger emissions.

17 pages, 16 figures, 2 appendices. Updated with corrected results for free-neutron decay

References in corpus (115)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• Shapiro delay measurement of a two solar mass neutron star
• A Massive Pulsar in a Compact Relativistic Binary
• GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs
• GW190425: Observation of a Compact Binary Coalescence with Total Mass $\sim 3.4M_{\odot }$
• Relativistic Shapiro delay measurements of an extremely massive millisecond pulsar
• Properties of the binary neutron star merger GW170817
• Electromagnetic Counterparts of Compact Object Mergers Powered by the Radioactive Decay of R-process Nuclei
• Composition and thermodynamics of nuclear matter with light clusters
• The Nuclear Equation of State and Neutron Star Masses
• Evolutions in 3D numerical relativity using fixed mesh refinement
• Statistical Model for a Complete Supernova Equation of State
• The Einstein Toolkit: A Community Computational Infrastructure for Relativistic Astrophysics
• Neutrino-driven winds from neutron star merger remnants
• Radiative Transfer Simulations for Neutron Star Merger Ejecta
• Kilonovae
• Binary Neutron Star Mergers: Mass Ejection, Electromagnetic Counterparts and Nucleosynthesis
• Refined Neutron-Star Mass Determinations for Six Eclipsing X-Ray Pulsar Binaries
• Red or blue? A potential kilonova imprint of the delay until black hole formation following a neutron star merger
• Radio Remnants of Compact Binary Mergers - the Electromagnetic Signal that will follow the Gravitational Waves
• Dynamical Mass Ejection from Binary Neutron Star Mergers
• Merger of binary neutron stars to a black hole: Disk mass, short gamma-ray bursts, and quasinormal mode ringing
• Neutrino signatures and the neutrino-driven wind in Binary Neutron Star Mergers
• Radioactivity and thermalization in the ejecta of compact object mergers and their impact on kilonova light curves
• On the Mass Distribution and Birth Masses of Neutron Stars
• The Neutron Star Mass Distribution
• Binary Neutron Star Mergers: Dependence on the Nuclear Equation of State
• Prompt merger collapse and the maximum mass of neutron stars
• Quasiequilibrium sequences of synchronized and irrotational binary neutron stars in general relativity. I. Method and tests
• The long-term evolution of neutron star merger remnants - I. The impact of r-process nucleosynthesis
• Constraint violation in free evolution schemes: comparing BSSNOK with a conformal decomposition of Z4
• Neutrino-driven winds in the aftermath of a neutron star merger: nucleosynthesis and electromagnetic transients
• Pulsar J0453+1559: A Double Neutron Star System with a Large Mass Asymmetry
• AT2017gfo: an anisotropic and three-component kilonova counterpart of GW170817
• Accurate evolutions of unequal-mass neutron-star binaries: properties of the torus and short GRB engines
• r-Process Lanthanide Production and Heating Rates in Kilonovae
• Global simulations of strongly magnetized remnant massive neutron stars formed in binary neutron star mergers
• The Dynamics of Binary Neutron Star Mergers and of GW170817
• Impact of ejecta morphology and composition on the electromagnetic signatures of neutron star mergers
• Time-Dependent Models of Accretion Disks Formed from Compact Object Mergers
• THC: a new high-order finite-difference high-resolution shock-capturing code for special-relativistic hydrodynamics
• Low mass binary neutron star mergers : gravitational waves and neutrino emission
• Compact binary evolutions with the Z4c formulation
• Gravitational waves and mass ejecta from binary neutron star mergers: Effect of the mass-ratio
• Merger of binary neutron stars of unequal mass in full general relativity
• Neutrino heating near hyper-accreting black holes
• The first direct double neutron star merger detection: implications for cosmic nucleosynthesis
• Neutron-powered precursors of kilonovae
• High-Order Fully General-Relativistic Hydrodynamics: new Approaches and Tests
• Cobalt-56 gamma-ray emission lines from the type Ia supernova 2014J
• Impact of an improved neutrino energy estimate on outflows in neutron star merger simulations
• Beyond second-order convergence in simulations of binary neutron stars in full general-relativity
• Unequal mass binary neutron star mergers and multimessenger signals
• SkyNet: A modular nuclear reaction network library
• Thermodynamics conditions of matter in neutron star mergers
• Longterm general relativistic simulation of binary neutron stars collapsing to a black hole
• General-Relativistic Large-Eddy Simulations of Binary Neutron Star Mergers
• Numerical Relativity Simulations of the Neutron Star Merger GW170817: Long-Term Remnant Evolutions, Winds, Remnant Disks, and Nucleosynthesis
• Chemical evolution with rotating massive star yields II. A new assessment of the solar s- and r- process components
• Implementation of a simplified approach to radiative transfer in general relativity
• Impact of weak interactions of free nucleons on the r-process in dynamical ejecta from neutron-star mergers
• Relativistic Simulations of Eccentric Binary Neutron Star Mergers: One-arm Spiral Instability and Effects of Neutron Star Spin
• Phase transitions and He-synthesis driven winds in neutrino cooled accretion disks: prospects for late flares in short gamma-ray bursts
• A magnetar engine for short GRBs and kilonovae
• Accretion-induced prompt black hole formation in asymmetric neutron star mergers, dynamical ejecta and kilonova signals
• On the maximum mass of neutron stars and GW190814
• Synchrotron radiation from the fast tail of dynamical ejecta of neutron star mergers
• Binary Neutron Stars with Generic Spin, Eccentricity, Mass ratio, and Compactness - Quasi-equilibrium Sequences and First Evolutions
• Mass ejection from disks surrounding a low-mass black hole: Viscous neutrino-radiation hydrodynamics simulation in full general relativity
• Equation of state of dense nuclear matter and neutron star structure from nuclear chiral interactions
• The One-Armed Spiral Instability in Neutron Star Mergers and its Detectability in Gravitational Waves
• How loud are neutron star mergers?
• One-arm Spiral Instability in Hypermassive Neutron Stars Formed by Dynamical-Capture Binary Neutron Star Mergers
• Spiral-wave wind for the blue kilonova
• Radioactive heating rate of r-process elements and macronova light curve
• Radio Counterparts of Compact Binary Mergers detectable in Gravitational Waves: A Simulation for an Optimized Survey
• Formation and Coalescence of Cosmological Supermassive Black Hole Binaries in Supermassive Star Collapse
• Evidence for X-ray Emission in Excess to the Jet Afterglow Decay 3.5 yrs After the Binary Neutron Star Merger GW 170817: A New Emission Component
• Three-Dimensional General-Relativistic Hydrodynamic Simulations of Binary Neutron Star Coalescence and Stellar Collapse with Multipatch Grids
• Monte-Carlo neutrino transport in neutron star merger simulations
• Production of very light elements and strontium in the early ejecta of neutron star mergers
• End-to-end kilonova models of neutron-star mergers with delayed black-hole formation
• Radioactive Heating and Late Time Kilonova Light Curves
• PSR J1930-1852: a pulsar in the widest known orbit around another neutron star
• Self-consistent picture of the mass ejection from a one second-long binary neutron star merger leaving a short-lived remnant in general-relativistic neutrino-radiation magnetohydrodynamic simulation
• Binary neutron star merger simulations with neutrino transport and turbulent viscosity: impact of different schemes and grid resolution
• Can jets make the radioactively powered emission from neutron star mergers bluer?
• Numerical relativity simulations of prompt collapse mergers: threshold mass and phenomenological constraints on neutron star properties after GW170817
• Asymmetric mass ratios for bright double neutron-star mergers
• Thermodynamics conditions of matter in the neutrino decoupling region during neutron star mergers
• Unequal Mass Binary Neutron Star Simulations with Neutrino Transport: Ejecta and Neutrino Emission
• Neutrino pair annihilation above merger remnants: implications of a long-lived massive neutron star
• GRMHD simulations of neutron-star mergers with weak interactions: r-process nucleosynthesis and electromagnetic signatures of dynamical ejecta
• Microscopic equation of state of hot nuclear matter for numerical relativity simulations
• Binary Neutron Star Merger Simulations with a Calibrated Turbulence Model
• Probing the incompressibility of nuclear matter at ultra-high density through the prompt collapse of asymmetric neutron star binaries
• Gamma-rays from kilonova: a potential probe of r-process nucleosynthesis
• Dynamical ejecta synchrotron emission as possible contributor to the changing behaviour of GRB170817A
• Self-consistent 3D radiative transfer for kilonovae: directional spectra from merger simulations
• Estimating outflow masses and velocities in merger simulations: impact of r-process heating and neutrino cooling
• Hyper-accreting black holes
• 3D radiative transfer kilonova modelling for binary neutron star merger simulations
• Ab-Initio General-Relativistic Neutrino-Radiation Hydrodynamics Simulations of Long-Lived Neutron Star Merger Remnants to Neutrino Cooling Timescales
• Radiation hydrodynamics modeling of kilonovae with SNEC
• Properties of gamma-ray decay lines in 3D core-collapse supernova models, with application to SN 1987A and Cas A
• Numerical-Relativity-Informed Effective-One-Body model for Black-Hole-Neutron-Star Mergers with Higher Modes and Spin Precession
• Electromagnetic counterparts of binary neutron star mergers leading to a strongly magnetized long-lived remnant neutron star
• Non-thermal emission from mildly relativistic dynamical ejecta of neutron star mergers
• Radio Afterglows from Compact Binary Coalescences: Prospects for Next-Generation Telescopes
• Geometric and thermodynamic characterization of binary neutron star accretion discs
• Effects of nuclear matter properties in neutron star mergers
• Impact of nuclear matter properties on the nucleosynthesis and the kilonova from binary neutron star merger ejecta
• Secular Outflows from Long-Lived Neutron Star Merger Remnants
• Revealing Phase Transition in Dense Matter with Gravitational Wave Spectroscopy of Binary Neutron Star Mergers
• Did a Kilonova Set Off in Our Galactic Backyard 3.5 Myr ago?

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• Proton-rich production of lanthanides: the $\nu i$ process
• Kilohertz Gravitational Waves from Binary Neutron Star Mergers: Full Spectrum Analyses and High-density Constraints on Neutron Star Matter
• Three-dimensional equation of state extension of quark matter in Fermi-liquid theory