Impact of in situ nuclear networks and atomic opacities on neutron star merger ejecta dynamics, nucleosynthesis, and kilonovae
arXiv:2512.11032 · doi:10.1051/0004-6361/202558682
Abstract
Modeling binary neutron star merger (BNSM) ejecta evolution requires simulations involving hydrodynamics, nuclear reactions, and radiative processes. The impact of nuclear burning and atomic opacity is poorly understood and often treated with simplified prescriptions. We systematically investigate different treatments of nuclear heating, thermalization, and opacities in radiation-hydrodynamics simulations of BNSM ejecta and kilonova light curves. Ejecta from long-term numerical-relativity simulations are evolved to ~30 days using a 2D ray-by-ray approach. We compare simplified heating-rates, thermalization prescriptions, and gray opacities with in-situ nuclear networks (NN) that track energy deposition, and include a composition-dependent thermalization scheme and frequency-dependent, atomic-physics-based opacities. Coupling NN and hydrodynamics affects nucleosynthesis and kilonova emission. Assuming homologous expansion alters the abundance evolution and produces a narrower second -process peak and a third peak shifted to higher mass numbers. Nuclear heating back-reaction delays and reddens the early emission. A constant thermalization underestimates the early luminosity and overestimates the late emission. Analytical opacities yield dimmer and redder kilonovae at early times ( hour) and a prolonged emission at days. Resolving the first hundreds of milliseconds of hydrodynamics is essential for robust nucleosynthesis calculations, and composition-dependent thermalization and frequency-dependent, atomic opacities are needed to accurately capture the ejecta temperature and kilonova brightness and color evolution. Analytic nuclear-power fits with simplified thermalization and opacities can reproduce the density and temperature evolution of the ejecta. [Abridged].
23 pages, 20 figures
References in corpus (41)
- GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
- Multi-messenger Observations of a Binary Neutron Star Merger
- Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
- Origin of the heavy elements in binary neutron-star mergers from a gravitational wave event
- Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source
- INTEGRAL Detection of the First Prompt Gamma-Ray Signal Coincident with the Gravitational Wave Event GW170817
- Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis
- A Kilonova Following a Long-Duration Gamma-Ray Burst at 350 Mpc
- A nearby long gamma-ray burst from a merger of compact objects
- AT2017gfo: an anisotropic and three-component kilonova counterpart of GW170817
- SkyNet: A modular nuclear reaction network library
- Numerical Relativity Simulations of the Neutron Star Merger GW170817: Long-Term Remnant Evolutions, Winds, Remnant Disks, and Nucleosynthesis
- Equation of state constraints from the threshold binary mass for prompt collapse of neutron star mergers
- Neutron Star Merger Remnants
- Axisymmetric Radiative Transfer Models of Kilonovae
- Kilonovae across the nuclear physics landscape: The impact of nuclear physics uncertainties on r-process-powered emission
- Post-merger Mass Ejection of Low-mass Binary Neutron Stars
- Modelling the spectra of the kilonova AT2017gfo -- I: The photospheric epochs
- Monte-Carlo neutrino transport in neutron star merger simulations
- Production of very light elements and strontium in the early ejecta of neutron star mergers
- 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?
- A low-mass binary neutron star: long-term ejecta evolution and kilonovae with weak blue emission
- 129I and 247Cm in Meteorites Constrain the Last Astrophysical Source of Solar r-process Elements
- NLTE Effects on Kilonova Expansion Opacities
- 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
- Self-consistent 3D radiative transfer for kilonovae: directional spectra from merger simulations
- 3D radiative transfer kilonova modelling for binary neutron star merger simulations
- Actinide opacities for modeling the spectra and light curves of kilonovae
- Radiation hydrodynamics modeling of kilonovae with SNEC
- -process nucleosynthesis from compact binary mergers
- Performance-Portable Binary Neutron Star Mergers with AthenaK
- Actinide signatures in low electron fraction kilonova ejecta
- Influence of neutrino-electron scattering and neutrino-pair annihilation on hypermassive neutron star
- Element formation in radiation-hydrodynamics simulations of kilonovae
- Cocoon shock breakout emission from binary neutron star mergers
- Did a Kilonova Set Off in Our Galactic Backyard 3.5 Myr ago?
- The impact of mass uncertainties on the r-process nucleosynthesis in neutron star mergers
- 2D End-to-End Modeling of Kilonovae from Binary Neutron Star Merger Remnants