Periodic Reporting for period 2 - KILONOVA (Probing r-process nucleosynthesis through its electromagnetic signatures)
Período documentado: 2022-07-01 hasta 2023-12-31
The lightest chemical elements –Hydrogen and Helium– were created about a minute after the Big Bang. Elements up to Iron are forged by fusion reactions in stars. Heavy elements between Iron and Uranium are produced by a sequence of neutron captures and beta-decays known as rapid neutron capture or r process. The freshly synthesized r-process elements undergo radioactive decay through various channels depositing energy in the ejecta that powers an optical/infrared transient called “kilonova” whose basic properties like luminosity and its dependence on ejecta mass, velocity, radioactive energy input, and atomic opacities have been dramatically confirmed by the observation of a kilonova electromagnetic transient associated with the gravitational wave signal GW170817. It provided the first direct indication that r-process elements are produced in neutron-star mergers. Additional events are expected to be detected in the following years, representing a complete change of paradigm in r-process research as for the first time we will be confronted with direct observational data. To fully exploit such opportunity, it is fundamental to combine an improved description of exotic neutron-rich nuclei involved in the r-process with sophisticated astrophysical simulations to provide accurate prediction of r-process nucleosynthesis yields and their electromagnetic signals to be confronted with observational data. We will further exploit the unique experimental capabilities of the GSI/FAIR facility, to advance our understanding of r-process nucleosynthesis and determine the contribution of mergers to the chemical enrichment of the galaxy in heavy elements.
We have advanced the description of beta-decays for r-process nuclei by including many-body correlations beyond mean-field and consistently treating Gamow-Teller and forbidden transitions. In addition, fission observables have been computed for a broad range of functionals and will be combined with the beta-decay calculations to obtain a full description of all fission reactions relevant for the r-process. Simulations that follow the long-term evolution of matter and account for all possible ejecta components have been performed including predictions of the nucleosynthesis and kilonova light curves and the relation with the lifetime of the central remnant. Systematic calculations of atomic opacities are in progress for all r-process elements. We have developed a complete simulation pipeline that combines. nuclear and atomic microphysics input with hydrodynamic ejecta models and nucleosynthesis predictions to perform radiative transfer calculations of kilonova spectra. First 3D self-consistent kilonova spectra have been computed that use tens of millions of lines. Finally, we have shown the strong impact of neutrinos in nucleosynthesis and demonstrated that in specific cases they can drive a novel nucleosynthesis process that we have denoted vr-process.
Our work on 3D self-consistent kilonova spectra based on Monte Carlo radiative transfer goes beyond current state of the art. Our goal is to identify what are the main elements contributing to the spectra and their dependence with the conditions achieved in the ejecta. This will allow to use kilonova observations to benchmark and characterize simulations and determine the dynamics and properties of the ejected material from observations. To achieve this goal, it is fundamental to address the sensitivity of the results to nuclear physics by including our new sets of beta-decay and fission rates in nucleosynthesis studies.
We had discovered a novel nucleosynthesis process denoted vr-process and plan to characterize its sensitivity to the astrophysical conditions and nuclear physics input with the goal to identify the astrophysical conditions under which it may operate.
We had discovered a novel nucleosynthesis process denoted vr-process and plan to characterize its sensitivity to the astrophysical conditions and nuclear physics input with the goal to identify the astrophysical conditions under which it may operate.