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arxiv: 2604.04362 · v1 · submitted 2026-04-06 · 🌌 astro-ph.HE

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A comparison of three neodymium atomic data sets for kilonova modeling

Christopher J. Fontes , Nicholas Vieira , Chris L. Fryer , Adithan Kathirgamaraju , Oleg Korobkin , Marko Risti\'c , Ryan T. Wollaeger
Authors on Pith no claims yet

Pith reviewed 2026-05-10 20:18 UTC · model grok-4.3

classification 🌌 astro-ph.HE
keywords kilonovaneodymiumatomic datalight curvesspectraradiative transferlanthanideskilonova modeling
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The pith

Different atomic data sets for neodymium produce kilonova light curves differing by a factor of nearly 1.5 in peak luminosity.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper compares three sets of atomic data for neodymium in fixed radiative transfer simulations of a simple 1D kilonova containing only that element. Data from the LANL codes, HULLAC, and Autostructure are swapped while the SuperNu Monte Carlo method stays the same. The resulting light curves and spectra differ substantially, with peak bolometric luminosities varying by a ratio of almost 1.5 and clear structural changes in the near- and mid-infrared that trace mainly to neutral Nd I. An extra LANL set calibrated to NIST energies further shifts late-time infrared features. These outcomes matter because kilonovae are primary sites for heavy-element formation, and atomic-physics choices directly affect what observers can infer from events like AT2017gfo.

Core claim

Using atomic data generated by the LANL suite, HULLAC, and Autostructure in a semi-analytic 1D kilonova model with a pure Nd atmosphere produces light curves whose peak bolometric luminosities differ by a ratio of nearly 1.5, along with significant differences in near- to mid-IR spectral structure that are attributed to the choice of atomic data for neutral Nd I. An additional LANL data set calibrated to NIST values also alters the IR spectral structure at late times.

What carries the argument

The SuperNu Monte Carlo radiative transfer code run on a fixed semi-analytic 1D kilonova model with a pure neodymium atmosphere, swapping input atomic data sets from three codes while holding all other physics constant.

If this is right

  • Atomic-physics uncertainties for even a single lanthanide must be treated carefully when modeling kilonovae from AT2017gfo onward.
  • Calibration of atomic energies to NIST values can change interpretations of late-time infrared spectra.
  • Observable differences from atomic data choices may affect derived kilonova parameters such as ejecta mass and velocity.
  • Improved atomic data libraries for lanthanides are needed to reduce scatter in predicted light curves and spectra.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The same atomic-data sensitivity is likely present in multi-element kilonova models and could affect total heavy-element yield estimates from neutron-star mergers.
  • Future infrared observations with facilities such as JWST could distinguish which atomic data set better reproduces real events.
  • Comparable sensitivity tests for other lanthanides might show even larger cumulative effects on kilonova predictions.

Load-bearing premise

A simple semi-analytic 1D kilonova model with a pure Nd atmosphere is sufficient to isolate and quantify the impact of atomic data variations on observables.

What would settle it

High-resolution near- and mid-infrared spectra of a real kilonova event that match the specific structural differences predicted by one data set but not the others would confirm or refute the modeled sensitivity.

Figures

Figures reproduced from arXiv: 2604.04362 by Adithan Kathirgamaraju, Chris L. Fryer, Christopher J. Fontes, Marko Risti\'c, Nicholas Vieira, Oleg Korobkin, Ryan T. Wollaeger.

Figure 1
Figure 1. Figure 1: Matter temperature versus velocity coordinate at day 1, 2, 3, 5, 8, and 11 (left to right, top to bottom) for the KN simulation, using LANL (solid), JLG (dashed) and Autostructure (dotted). The temperature profiles produced by all three data sets are in close agreement until day 5, when they start to deviate at outer radii. This discrepancy between calculations moves inward with time, following the inward-… view at source ↗
Figure 2
Figure 2. Figure 2: Ionization fraction versus velocity coordinate at day 1, 2, 3, 5, 8, and 11 (left to right, top to bottom) for the KN simulation, using LANL (solid), JLG (dashed) and Autostructure (dotted). Ionization trends agree throughout time for all three data sets: all four ion stages are present by day 1 and by day 5 only Nd II and Nd I remain, with Nd II recombining to Nd I. All results are computed with the Saha … view at source ↗
Figure 3
Figure 3. Figure 3: Bolometric luminosity (left) and broadband magnitudes (right) versus time, for LANL (solid), JLG (dashed) and Autostructure (dotted) data sets. Bolometric luminosities are comparable in order of magnitude; optical band magnitudes notably decay at distinct rates depending on the data set, with the LANL data set showing the steepest decline. configuration to Nd I significantly affects the spectrum at each ti… view at source ↗
Figure 4
Figure 4. Figure 4: Spectra versus wavelength at day 2 (upper left), day 5 (upper right), day 8 (lower left) and day 11 (lower right), for LANL (solid), JLG (dashed) and Autostructure (dotted) data sets. Bulk emission agrees well among all three data sets at early time, but all spectra diverge at late time, when Nd I begins to dominate the ionization population. All spectra show significant discrepancy. The LANL data set has … view at source ↗
Figure 5
Figure 5. Figure 5: Same as [PITH_FULL_IMAGE:figures/full_fig_p015_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Same as [PITH_FULL_IMAGE:figures/full_fig_p016_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Same as [PITH_FULL_IMAGE:figures/full_fig_p017_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Spectra versus wavelength at day 2 (upper left), day 5 (upper right), day 8 (lower left) and day 11 (lower right), for uncalibrated LANL (solid), calibrated NIST-LANL (dashed) data sets, and NIST-LANL data with 4f 3 5d 2 6s 1 added to Nd I (dotted). The addition of the 4f 3 5d 2 6s 1 configuration to Nd I significantly affects the spectrum at each time shown. Kato, D., Murakami, I., Tanaka, M., et al. 2021… view at source ↗
read the original 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.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The manuscript compares the impact of three neodymium atomic data sets (LANL, HULLAC, Autostructure) on kilonova light curves and spectra by holding the SuperNu Monte Carlo radiative transfer code and a simple 1D semi-analytic pure-Nd ejecta model fixed while swapping only the input atomic data. It reports that the data choice produces order-unity differences, with peak bolometric luminosities differing by a factor of nearly 1.5 between the HULLAC/Autostructure and LANL sets, plus significant near- to mid-IR spectral variations attributed primarily to neutral Nd I. A calibrated version of the LANL dataset is also presented and shown to affect late-time IR structure.

Significance. If the results hold, the work demonstrates the substantial sensitivity of kilonova observables to atomic physics inputs for a key lanthanide, directly relevant to modeling AT2017gfo and future events. Its primary strength is the controlled numerical experiment that isolates atomic data variations while fixing the radiative transfer solver and ejecta structure, enabling clear attribution of differences without confounding factors. This provides a concrete, falsifiable illustration of atomic data uncertainties that the community can build upon.

minor comments (3)
  1. Abstract: the statement that peak luminosities 'differ by a ratio of nearly 1.5' would be more precise if the exact peak values (in erg/s) for each of the three datasets were stated explicitly rather than only the ratio.
  2. The attribution of IR spectral differences to Nd I (mentioned in the abstract and results) would be strengthened by a brief quantitative comparison of the number of levels or transitions included for Nd I in each dataset, perhaps in a table.
  3. The calibration procedure for the additional LANL dataset (energies matched to NIST) is described only at a high level; a short appendix or paragraph detailing which levels were adjusted and by how much would improve reproducibility.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of our manuscript, including the recognition of our controlled numerical experiment isolating the effects of different neodymium atomic data sets while holding the SuperNu code and ejecta model fixed. We appreciate the recommendation for minor revision and the acknowledgment that the work provides a concrete illustration of atomic data uncertainties relevant to kilonova modeling.

Circularity Check

0 steps flagged

No significant circularity

full rationale

The paper performs a controlled numerical comparison of kilonova light curves and spectra by holding the SuperNu Monte Carlo radiative transfer solver and the 1D semi-analytic ejecta model fixed while swapping only the input neodymium atomic data sets (LANL, HULLAC, Autostructure) and one calibrated variant. Reported differences, such as the factor of ~1.5 in peak bolometric luminosity and IR spectral variations attributed to Nd I, are direct outputs of these simulations with no derivations, parameter fittings, or predictions that reduce to the inputs by construction. No self-citation load-bearing steps, uniqueness theorems, or ansatzes are invoked; the central claim follows straightforwardly from the experimental design without circular reduction.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The study relies on the outputs of three established atomic physics codes and a standard semi-analytic kilonova model; no new free parameters, axioms beyond domain standards, or invented entities are introduced.

axioms (2)
  • domain assumption Atomic data generated by LANL, HULLAC, and Autostructure codes are computed using standard atomic physics approximations appropriate for Nd.
    The paper treats these code outputs as interchangeable inputs whose differences drive observable changes.
  • domain assumption The semi-analytic 1D pure-Nd kilonova atmosphere model isolates the effect of atomic data on radiative transfer.
    Used to hold all other physics fixed while varying only the atomic data.

pith-pipeline@v0.9.0 · 5612 in / 1463 out tokens · 36348 ms · 2026-05-10T20:18:40.421998+00:00 · methodology

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Reference graph

Works this paper leans on

4 extracted references · 4 canonical work pages

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    Abdallah Jr, J., Clark, R. E. H., & Cowan, R. D. 1988, Los Alamos Manual LA-11436-M, Vol. I, Tech. rep. Abdikamalov, E., Burrows, A., Ott, C. D., et al. 2012, ApJ, 755, 111, doi: 10.1088/0004-637X/755/2/111 Arcavi, I., Hosseinzadeh, G., Howell, D. A., et al. 2017, Nature, 551, 64, doi: 10.1038/nature24291 Badnell, N. R. 2011, Computer Physics Communicatio...

    work page doi:10.1088/0004-637x/755/2/111 1988

  2. [2]

    2023, Monthly Notices of the Royal Astronomical Society, 520, 2558, doi: 10.1093/mnras/stad232

    JLG Autostructure Figure 6.Same as Figure 4, but with LANL data with minimized level and line list data for Nd I (NN-LANL). At day 2, we see that NN-LANL data produces a bluer spectrum between 1000 and 10000 ˚A. Additionally, much of the mid-IR line structure is removed, resembling the spectra of the other data sets. Bulla, M. 2023, MNRAS, 520, 2558, doi:...

    work page doi:10.1093/mnras/stad232 2023

  3. [3]

    At days 2 and 5 the specta are dim compared to those of the original LANL data set

    JLG Autostructure Figure 7.Same as Figure 4, but with LANL data calibrated to the NIST database (Section 2.1.1). At days 2 and 5 the specta are dim compared to those of the original LANL data set. Similar to the NN-LANL data set in Figure 6, where the neutral stage has been effectively removed, we observe that the calibration significantly effects mid-IR ...

    work page doi:10.1093/mnras/stac2792 2023

  4. [4]

    e L., Rynkun P., 2024, @doi [ ] 10.1093/mnras/stae2504 , https://ui.adsabs.harvard.edu/abs/2024MNRAS.535.2670K 535, 2670

    NIST-LANL (fc = 10 3, 4f35d26s1) Figure 8.Spectra versus wavelength at day 2 (upper left), day 5 (upper right), day 8 (lower left) and day 11 (lower right), for uncalibrated LANL (solid), calibrated NIST-LANL (dashed) data sets, and NIST-LANL data with 4f 35d26s1 added to Nd I (dotted). The addition of the 4f 35d26s1 configuration to Nd I significantly af...

    work page doi:10.1093/mnras/stae2504 2021