The outflows from neutrino-cooled black-hole (BH) accretion disks formed in neutron-star mergers or cores of collapsing stars are expected to be neutron-rich enough explain a large fraction elements created by the rapid neutron-capture (r-) process, but their precise chemical composition remains elusive. Here, we investigate role fast neutrino flavor conversion, motivated findings our post-processing analysis that shows evidence electron-neutrino lepton-number (ELN) crossings deep inside...

We implement a multi-group and discrete-ordinate neutrino transport model in spherical symmetry which allows to simulate collective oscillations by including realistic collisional rates self-consistent way. utilize this innovative model, based on strategic parameter rescaling, study recently proposed flavor instability caused the asymmetry of emission absorption between $\nu_e$ $\bar\nu_e$ for four different static backgrounds taken from stages core-collapse supernova simulation. Our results...

We consider $r$-process nucleosynthesis in outflows from black hole accretion discs formed double neutron star and -- mergers. These outflows, powered by angular momentum transport processes nuclear recombination, represent an important some cases dominant contribution to the total mass ejected merger. Here we calculate yields disc using thermodynamic trajectories hydrodynamic simulations, coupled a reaction network. find that produce robust abundance pattern around second peak (mass number...

We have performed $r$-process calculations for matter ejected dynamically in neutron star mergers based on a complete set of trajectories from three-dimensional relativistic smoothed particle hydrodynamic simulation with total mass $\ensuremath{\sim}1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{M}_{\ensuremath{\bigodot}}$. Our consider an extended nuclear network, including spontaneous, $\ensuremath{\beta}$- and neutron-induced fission adopting yield distributions the abla...

One of the most promising electromagnetic signatures compact object mergers are kilonovae: approximately isotropic radioactively-powered transients that peak days to weeks post-merger. Key uncertainties in modeling kilonovae include emission profiles radioactive decay products---non-thermal beta- and alpha-particles, fission fragments, gamma-rays---and efficiency with which they deposit their energy ejecta. The total its thermalization sets luminosity budget is therefore necessary for...

The massive neutron star (NS) or black hole (BH) accretion disk resulting from NS--NS NS--BH mergers is dense in neutrinos. We present the first study on role of angular distributions neutrino flavor conversion above remnant disk. In particular, we focus "fast" pairwise conversions whose rate depends local intensity electron lepton number carried by Because emission geometry and flux density $\bar{\nu}_e$ being larger than that $\nu_e$, fast prove to be a generic phenomenon for physically...

The kilonova emission observed following the binary neutron star merger event GW170817 provided first direct evidence for synthesis of heavy nuclei through r-process. late-time transition in spectral energy distribution to near-infrared wavelengths was interpreted as indicating production lanthanide nuclei, with atomic mass number A>140. However, compelling presence heavier third-peak r-process elements (e.g., gold, platinum) or translead remains elusive. At early times (~days) most heating...

The remnant of neutron star mergers is dense in neutrinos. By employing inputs from one hydrodynamical simulation a binary merger with black hole $3\ M_\odot$ the center, dimensionless spin parameter $0.8$ and an accretion torus $0.3\ M_\odot$, neutrino emission properties are investigated as evolves. Initially, local number density $\bar{\nu}_e$ larger than that $\nu_e$ everywhere above remnant. Then, approaches self-regulated equilibrium, abundance neutrinos overcomes antineutrinos funnel...

Neutrinos emitted in the coalescence of two neutron stars affect dynamics outflow ejecta and nucleosynthesis heavy elements. In this work, we analyze neutrino emission properties conditions leading to growth flavor instabilities merger remnants consisting a hypermassive star an accretion disk during first 10 ms after merger. The analyses are based on hydrodynamical simulations that include modeling absorption effects via "Improved Leakage-Equilibration-Absorption Scheme" (ILEAS). We also...

We perform numerical simulations of fast collective neutrino flavor conversions in an one-dimensional box mimicking a system with the periodic boundary condition one spatial direction and translation symmetry other two dimensions. evolve over several thousands characteristic timescale (inverse interaction strength) different initial $\bar\nu_e$ to $\nu_e$ number density ratios seed perturbations. find that small scale structures are formed due waves. This results nearly depolarization...

The fast flavor instability (FFI) is expected to be ubiquitous in core-collapse supernovae and neutron star mergers. It rapidly shuffles neutrino a way that could impact the explosion mechanism, signals, mass outflows, nucleosynthesis. variety of initial conditions simulation methods employed simulations FFI prevent an apples-to-apples comparison results. We simulate standardized test problem using five independent codes verify they are all faithfully simulating underlying quantum kinetic...

The fast flavor conversions (FFCs) of neutrinos generally exist in core-collapse supernovae and binary neutron-star merger remnants can significantly change the composition affect dynamics nucleosynthesis processes. Several analytical prescriptions were proposed recently to approximately explain or predict asymptotic outcome FFCs for systems with different initial boundary conditions, aim providing better understandings practical implementation hydrodynamic modeling. In this work, we obtain...

Charged-current neutrino processes such as ${\ensuremath{\nu}}_{e}+n\ensuremath{\rightleftharpoons}p+{e}^{\ensuremath{-}}$ and ${\overline{\ensuremath{\nu}}}_{e}+p\ensuremath{\rightleftharpoons}n+{e}^{+}$ destroy the flavor coherence among weak-interaction states of a single thus damp its oscillation. In dense gas that inside core-collapse supernova or black hole accretion disk formed in compact binary merger, however, these ``collision'' can trigger large conversion cooperation with strong...

We estimate the long-lasting gravitational wave (GW) emission of compact dark objects following a binary neutron-star (NS) merger. consider objects, which initially reside in centers NSs and may consist self-interacting matter (DM). By approximating as test particles, we model merging NS binaries hosting DM components with three-dimensional relativistic simulations. Our simulation results suggest that remain gravitationally bound orbit inside merger remnant orbital separations typically few...

Fast flavor conversions (FFCs) of neutrinos, which can occur in core-collapse supernovae (CCSNe), are multiangle effects. They depend on the angular distribution neutrino's electron lepton number (ELN). In this work, we present a comprehensive study FFCs by solving multienergy and quantum kinetic equations with an extended set collisional weak processes based static spherically symmetric CCSN matter background profile. We investigate emergence evolution models featuring different ELN...

In the most extreme astrophysical environments, such as core-collapse supernovae (CCSNe) and neutron star mergers (NSMs), neutrinos can undergo fast flavor conversions (FFCs) on exceedingly short scales. Intensive simulations have demonstrated that FFCs attain equilibrium states in certain models. this study, we utilize physics-informed neural networks (PINNs) to predict asymptotic outcomes of FFCs, by specifically targeting first two moments neutrino angular distributions. This makes our...

In this paper, we explore the effects of neutrino flavor oscillations on supernova nucleosynthesis and signals. Our study is based detailed information about spectra their time evolution from a spherically-symmetric model for an 18 M progenitor. We find that collective are not only sensitive to energy angular distributions at emission, but also both electron density profile. apply results impact signals Galactic supernova. show in our model, enhance production rare isotopes 138La 180Ta have...

We study the optical and near-infrared luminosities detectability of radioactively powered electromagnetic transients ('macronovae') occuring in aftermath binary neutron star black hole mergers. explore that result from dynamic ejecta those different types wind outflows. Based on full nuclear network simulations we calculate resulting light curves wavelength bands. scrutinize robustness results by comparing (a) two reaction networks (b) macronova models. particular how sensitive are to...

We show that for the active-sterile flavor mixing parameters suggested by reactor neutrino anomaly, substantial \\nu_e-\\nu_s and \bar \\nu_e-\bar \\nu_s conversion occurs in regions with electron fraction of \approx 1/3 near core an 8.8 M_sun electron-capture supernova. Compared to case without such conversion, neutron-richness ejected material is enhanced allow production elements from Sr, Y, Zr up Cd broad agreement observations metal-poor star HD 122563. Active-sterile also strongly...

We investigate the impact of charged-current--neutrino processes on formation and evolution neutrino spectra during deleptonization proto-neutron stars. To this end we develop full kinematics these reaction rates consistent with nuclear equation state, including weak magnetism contributions. This allows us to systematically study inelastic contributions ${\ensuremath{\nu}}_{e}$ ${\overline{\ensuremath{\nu}}}_{e}$ luminosities average energies. Furthermore, explore role inverse neutron decay,...

We propose a new constraint on light (sub-GeV) particles beyond the Standard Model that can be produced inside protoneutron star core resulting from core-collapse supernova explosion. It is derived by demanding energy carried exotic being transferred to progenitor stellar envelopes not exceed explosion of $\ensuremath{\lesssim}\text{ }2\ifmmode\times\else\texttimes\fi{}{10}^{51}\text{ }\text{ }\mathrm{erg}$ observed supernovae. show specifically for case dark photon which kinetically mixes...

A novel analysis is performed, incorporating time-of-flight (TOF) information to study the interactions of dark matter (DM) with standard model particles. After supernova (SN) explosions, DM mass m_{χ}≲O(MeV) in halo can be boosted by SN neutrinos (SNν) relativistic speed. The SNν (BDM) arrives on Earth TOF which depends only m_{χ} and independent cross section. These BDMs interact detector targets low-background experiments manifest as afterglow events after arrival SNν. characteristic...

Neutrinos can undergo fast flavor conversions (FFCs) within extremely dense astrophysical environments, such as core-collapse supernovae (CCSNe) and neutron star mergers (NSMs). In this study, we explore FFCs in a neutrino gas, revealing that when the FFC growth rate significantly exceeds of vacuum Hamiltonian, all neutrinos (regardless energy) share common survival probability dictated by energy-integrated spectrum. We then employ physics-informed neural networks (PINNs) to predict...