Nebular Emission from Lanthanide-rich Ejecta of Neutron Star Merger

Understand

The nebular phase of lanthanide-rich ejecta of a neutron star merger (NSM) is studied by using a one-zone model, in which the atomic properties are represented by a single species, neodymium (Nd).

• Under the assumption that beta-decay of r-process nuclei is the heat and ionization source, we solve the ionization and thermal balance of the ejecta under non-local thermodynamic equilibrium.
• The atomic data including energy levels, radiative transition rates, collision strengths, and recombination rate coefficients, are obtained by using atomic structure codes, GRASP2K and HULLAC.
• We find that both permitted and forbidden lines roughly equally contribute to the cooling rate of Nd II and Nd III at the nebular temperatures.