Shih-Jie Huang (NTU); Meng-Ru Wu (ASIoP)
R-process nucleosynthesis in material ejected from neutron star mergers radioactively power the ejecta, observed as kilonovae. Meanwhile, the nuclear energy release during the r-process can also affect ejecta dynamics, such as enhance the outflow mass from the accretion disc, or the mass of fall-back material that may power late-time gamma-ray emission. Thus, it is meaningful to consider the nucleosynthesis heating in the hydrodynamics simulation of kilonovae ejecta. Previous studies show that the dominant reactions in the r-process, neutron captures and photodissociation, may reach equilibrium for certain environmental conditions. Given the equilibrium, the isotopic abundances can be determined by a simple formula, which may be used to speed up the calculation of nucleosynthesis. In this project, we study when the equilibrium between neutron captures and photodissociation happens, and how fast the calculation can be speeded up.