When binary systems of neutron stars merge, a very small fraction their rest mass is ejected, either dynamically or secularly. This material neutron-rich and its nucleosynthesis provides the astrophysical site for production heavy elements in Universe, together with kilonova signal confirming neutron-star mergers as origin short gamma-ray bursts. We perform full general-relativistic simulations employing three different nuclear-physics equations state (EOSs), considering both equal-...

We probe the gravitational interaction of two black holes in strong-field regime by computing scattering angle $\ensuremath{\chi}$ hyperboliclike, close binary-black-hole encounters as a function impact parameter. The fully general-relativistic result from numerical relativity is compared to analytic approximations: post-Newtonian theory and effective-one-body formalism. As parameter decreases, so that pass within few times their Schwarzschild radii, we find prediction becomes quite...

Neutrinos are copiously emitted by neutron star mergers, due to the high temperatures reached dense matter during merger and its aftermath. influence dynamics shape properties of ejecta, including resulting $r$-process nucleosynthesis kilonova emission. In this work, we analyze neutrino emission from a large sample radiation hydrodynamics simulations in Numerical Relativity, covering broad range initial masses, nuclear equation state viscosity treatments. We extract luminosities mean...

GW190425 was the second gravitational wave (GW) signal compatible with a binary neutron star (BNS) merger detected by Advanced LIGO and Virgo detectors. Since no electromagnetic counterpart identified, whether associated kilonova too dim or localisation area broad is still an open question. We simulate 28 BNS mergers chirp mass of ratio $1 \leq q 1.67$, using numerical-relativity simulations finite temperature, composition dependent nuclear equation state (EOS) neutrino radiation. The energy...

We present a strongly hyperbolic first-order formulation of the Einstein equations based on conformal and covariant Z4 system (CCZ4) with constraint-violation damping, which we refer to as FO-CCZ4. As CCZ4, this combines advantages traceless formulation, suppression constraint violations given by damping terms, but being first order in time space, it is particularly suited for discontinuous Galerkin (DG) implementation. The has been obtained making careful use second-order ordering...

Accretion disks formed in binary neutron star mergers play a central role many astrophysical processes of interest, including the launching relativistic jets or ejection neutron-rich matter hosting heavy element nucleosynthesis. In this work we analyze detail properties accretion from 44 ab initio merger simulations for large set nuclear equations state, mass ratios, and remnant fates, with aim furnishing reliable initial conditions disk comprehensive characterization their properties. We...

Abstract The recent detection of the live isotopes 60 Fe and 244 Pu in deep ocean sediments dating back to past 3–4 Myr poses a serious challenge identification their production site(s). While is usually attributed standard core-collapse supernovae, actinides are r -process nucleosynthesis yields, which believed be synthesized rare events, such as special classes supernovae or binary mergers involving at least one neutron star. Previous works concluded that single star merger cannot explain...

Abstract We present entropy-limited hydrodynamics (ELH): a new approach for the computation of numerical fluxes arising in discretization hyperbolic equations conservation form. ELH is based on hybridisation an unfiltered high-order scheme with first-order Lax-Friedrichs method. The activation low-order part driven by measure locally generated entropy inspired artificial-viscosity method proposed Guermond et al. (J. Comput. Phys. 230(11):4248-4267, 2011, doi: 10.1016/j.jcp.2010.11.043 )....

ABSTRACT The dynamics in mergers of binary neutron star (BNS) systems depend sensitively on the equation state (EOS) dense matter. This has profound implications emission gravitational waves (GWs) and ejection matter merger post-merger phases is thus high interest for multimessenger astronomy. Today, a variety nuclear EOSs are available with various underlying microphysical models. calls study to focus EOS effects from different physical properties their influence BNS mergers. We perform...

The Einstein and Maxwell equations are both systems of hyperbolic which need to satisfy a set elliptic constraints throughout evolution. However, while electrodynamics (EM) magnetohydrodynamics (MHD) have benefited from large number evolution schemes that able enforce these easily applicable curvilinear coordinates, unstructured meshes, or N-body simulations, many techniques cannot be straightforwardly applied existing formulations the equations. We develop 3+1 formulation shows striking...

Accretion disks formed in binary neutron star mergers play a central role many astrophysical processes of interest, including the launching relativistic jets or ejection neutron-rich matter hosting heavy element nucleosynthesis. In this work we analyze detail properties accretion from 44 ab initio merger simulations for large set nuclear equations state, mass ratios and remnant fates, with aim furnishing reliable initial conditions disk comprehensive characterization their properties. We...

A realistic and detailed description of neutrinos in binary neutron star (BNS) mergers is essential to build reliable models such systems. To this end, we present BNS_NURATES, a novel open-source numerical library designed for the efficient on-the-fly computation neutrino interactions, with particular focus on regimes relevant BNS mergers. BNS_NURATES targets an higher level accuracy realism implementation commonly employed reactions by accounting microphysics effects as weak magnetism mean...

The dynamics in mergers of binary neutron star (BNS) systems depend sensitively on the equation state (EOS) dense matter. This has profound implications emission gravitational waves (GWs) and ejection matter merger post-merger phases is thus high interest for multi-messenger astronomy. Today, a variety nuclear EOSs are available with various underlying microphysical models. calls study to focus EOS effects from different physical properties their influence BNS mergers. We perform simulations...

The recent detection of the live isotopes $^{60}{\rm Fe}$ and $^{244}{\rm Pu}$ in deep ocean sediments dating back to past 3-4 Myr poses a serious challenge identification their production site(s). While is usually attributed standard core-collapse supernovae, actinides are r-process nucleosynthesis yields, which believed be synthesized rare events, such as special classes supernovae or binary mergers involving at least one neutron star. Previous works concluded that single star merger...

The main features of the gravitational dynamics binary neutron star systems are now well established. While inspiral can be precisely described in post-Newtonian approximation, fully relativistic magneto-hydrodynamical simulations required to model evolution merger and post-merger phase. However, interpretation numerical results often non-trivial, so that toy models become a very powerful tool. Not only do they simplify dynamics, but also allow gain insights into physics behind it. In this...

GW190425 was the second gravitational wave (GW) signal compatible with a binary neutron star (BNS) merger detected by Advanced LIGO and Virgo detectors. Since no electromagnetic counterpart identified, whether associated kilonova too dim or localisation area broad is still an open question. We simulate 28 BNS mergers chirp mass of ratio $1 \leq q 1.67$, using numerical-relativity simulations finite temperature, composition dependent nuclear equation state (EOS) neutrino radiation. The energy...