A comparison of three neodymium atomic data sets for kilonova modeling

TL;DR

This study investigates how different atomic data sets for neodymium influence kilonova light curves and spectra, revealing significant variations that underscore the importance of atomic physics accuracy in modeling these events.

Contribution

It compares three neodymium atomic data sets and demonstrates their substantial impact on kilonova observable predictions, highlighting the need for precise atomic data in astrophysical modeling.

Findings

Peak luminosities vary by a factor of 1.5 between data sets.

Spectral structures differ notably in the near- to mid-IR range.

Calibrating atomic energies affects late-time IR spectra.

Abstract

We examine the impact of input neodymium (Nd) atomic data on the light curves and spectra of kilonovae, probing the sensitivity of kilonova observables to the atomic physics of this important lanthanide element. We use the SuperNu Monte Carlo radiative transfer code, simulating a simple semi-analytic 1D kilonova with a pure Nd atmosphere, fixing the radiative transfer method while using input atomic data generated by three different codes: the LANL suite of atomic physics codes, HULLAC, and Autostructure. We see that the choice of atomic data significantly shapes the resulting light curves and spectra. Peak bolometric luminosities differ by a ratio of nearly 1.5 between HULLAC/Autostructure and LANL data sets. Moreover, we observe significant near- to mid-IR differences in the structure of the spectra. We specifically attribute these differences to the choice of atomic data for neutral Nd I. Many of the results here have been adapted from a presentation at "Radiative Transfer and Atomic Physics of Kilonovae" in Stockholm, 2023. We additionally present a LANL data set with energies calibrated to available values in the NIST Atomic Spectra Database, and demonstrate that this calibration also significantly affects IR spectral structure at late time. The substantial differences in kilonova observables that arise from tuning the atomic data of just one lanthanide element highlight the special attention that must be paid to atomic physics uncertainties when modeling kilonovae, from AT2017gfo to beyond.