Ce II-IV emission in kilonovae with R-matrix collision strengths and distorted wave recombination rates
Abstract
We provide transition probabilities and Maxwellian-averaged collision-strengths for the electron-impact excitation of Ce {\sc ii} - {\sc iv}. These ions are potentially abundant in kilonovae (KNe) and feature both forbidden and allowed transitions in the infrared. These atomic data are obtained using the {\sc grasp}0 atomic structure code, interfaced with the non-perturbative {\sc darc} R-matrix close-coupling codes. We additionally use {\sc autostructure} to produce dielectronic and radiative recombination rate coefficients for Ce {\sc ii} - {\sc vi}. Using this data, we calculate an approximate ionization balance including non-thermal ionization rates with deposition rates from realistic models. We find Ce {\sc ii} - {\sc iv} to be of roughly equal abundance, subject to ejecta conditions. We find that generally we need ≳ 10−3 M⊙ of Ce in total to produce emission of comparable luminosity to the features in the spectrum of AT2023vfi. In particular, it is found that [Ce {\sc iv}] 4.5 μm requires both strong ionization and weak recombination, as well as a production of Ce considerably stronger than that of the solar abundance in order to have luminosity comparable to the apparent emission in this wavelength vicinity in \grb. %which is seemingly incompatible with the current understanding of the bulk composition of KNe. With such strict requirements on individual element masses, the detection of individual lanthanides on a line-by-line basis in the nebular phase seems unlikely - but lanthanides may remain important for cooling and early time analyses.
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BibTeX
@misc{mulholland2026iiiv,
title = {{Ce II-IV emission in kilonovae with R-matrix collision strengths and distorted wave recombination rates}},
author = {Leo Patrick Mulholland and Niamh Ferguson and Luke J. Shingles and Catherine A. Ramsbottom and Connor P. Ballance and Stuart A. Sim},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.15900},
eprint = {2609.15900},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.15900},
}
RIS
TY - UNPB
TI - Ce II-IV emission in kilonovae with R-matrix collision strengths and distorted wave recombination rates
AU - Leo Patrick Mulholland
AU - Niamh Ferguson
AU - Luke J. Shingles
AU - Catherine A. Ramsbottom
AU - Connor P. Ballance
AU - Stuart A. Sim
PY - 2026
DA - 2026/09/14
PB - arXiv
DO - 10.48550/arxiv.2609.15900
UR - https://arxiv.org/abs/2609.15900
AB - We provide transition probabilities and Maxwellian-averaged collision-strengths for the electron-impact excitation of Ce {\sc ii} - {\sc iv}. These ions are potentially abundant in kilonovae (KNe) and feature both forbidden and allowed transitions in the infrared. These atomic data are obtained using the {\sc grasp}^0 atomic structure code, interfaced with the non-perturbative {\sc darc} R-matrix close-coupling codes. We additionally use {\sc autostructure} to produce dielectronic and radiative recombination rate coefficients for Ce {\sc ii} - {\sc vi}. Using this data, we calculate an approximate ionization balance including non-thermal ionization rates with deposition rates from realistic models. We find Ce {\sc ii} - {\sc iv} to be of roughly equal abundance, subject to ejecta conditions. We find that generally we need ≳ 10^−3 M_⊙ of Ce in total to produce emission of comparable luminosity to the features in the spectrum of AT2023vfi. In particular, it is found that [Ce {\sc iv}] 4.5 μm requires both strong ionization and weak recombination, as well as a production of Ce considerably stronger than that of the solar abundance in order to have luminosity comparable to the apparent emission in this wavelength vicinity in \grb. %which is seemingly incompatible with the current understanding of the bulk composition of KNe. With such strict requirements on individual element masses, the detection of individual lanthanides on a line-by-line basis in the nebular phase seems unlikely - but lanthanides may remain important for cooling and early time analyses.
ER -