Electron impact excitation of Te IV and V and Level Resolved R-matrix Photoionization of Te I - IV with application to modelling of AT2017gfo

TL;DR

This paper provides detailed atomic data for tellurium ions using advanced computational methods, aiding spectral modeling of kilonovae and exploring Te IV's role in observed emission features of AT2017gfo.

Contribution

It introduces new, accurate atomic data for Te IV and V ions using R-matrix and MCDHF methods, improving modeling of kilonova spectra.

Findings

Atomic data for Te IV and V computed with R-matrix and MCDHF methods.

Synthetic spectra show Te IV may contribute to the 1.08 μm emission in AT2017gfo.

Comparison with observations supports the potential role of Te in kilonova emission features.

Abstract

Spectral modelling of kilonovae (KNe) require large amounts of collisional excitation and photoionization atomic data for lowly ionised (neutral, singly and doubly ionised) species of heavy elements. Much of the data currently used is calculated using approximate hydrogenic results or adopts semi-empirical formulae. We present atomic data for ions of tellurium (Te) computed using the well-known $R$-matrix method. Results will also be presented for radiative and thermal collisions of Te IV and V, for which the required atomic data are also typically limited in the literature. The Multi-Configuration-Dirac-Hartree-Fock (MCDHF) method is used to produce model atomic structures and radiative rates. These model structures are then used to calculate electron-impact-excitation and photoionization cross-sections. The resulting excitation and radiative rates are further used in a collisional radiative model to produce synthetic spectra, which are compared with observations. We also investigate the possibility of Te IV contributing to the 1.08 $\mu$m emission feature in the mid-epochs of AT2017gfo alongside the established P-Cygni feature of Sr II.