REVIEW 4 major objections 4 minor 54 references
This paper claims to deliver a laboratory-grounded, uniformly validated set of near-infrared atomic lines (Y, J, H bands) for stellar abundance determinations, selected by a quantitative four-stage filter applied to six benchmark stars span
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · deepseek-v4-flash
2026-08-02 23:15 UTC pith:QPEYQE6X
load-bearing objection Good method, broken table: the printed line lists contradict the summary counts, so the central data product isn't usable until fixed. the 4 major comments →
Gaia FGK Benchmark Stars: Selecting Infrared Lines for Abundance Determination
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The central claim is that a set of atomic transitions in the near-infrared can be identified that behave consistently across a wide range of stellar parameters, so that they can be used for abundance determinations without object-dependent fine-tuning. The paper demonstrates this by applying a sequence of quantitative filters—line depth >=0.03, non-saturation via curve-of-growth slope and core-flux response, purity measured as the ratio of equivalent widths in two velocity windows, and goodness-of-fit statistics with band-specific thresholds—to synthetic spectra computed for six benchmark stars. The accepted lines are tabulated per spectral type in the appendices. The method is designed to b
What carries the argument
The key mechanism is a four-stage flagging decision tree. Each candidate transition is evaluated for depth (minimum central absorption 0.03), saturation (local curve-of-growth slope below 0.5 plus negligible core-flux change flags the line), purity (P = equivalent width in a 30 km/s window divided by that in a 60 km/s window; P>=0.75 accepted, 0.5–0.75 flagged undecided, <0.5 rejected), and goodness of fit (reduced chi-square, RMSE, and MAD against observed spectra, with relaxed thresholds in J and H bands to account for telluric residuals). Only lines that earn 'YYYY' in all four stages are included in the robust list.
Load-bearing premise
The entire selection rests on the assumption that the 1D-LTE synthetic spectra computed with benchmark parameters and scaled abundances are accurate enough that a line's failure to match the observed profile is due to the line itself, not to the model or assumed abundance.
What would settle it
Take a star not in the sample (or one with independently known elemental abundances) and measure abundances from the paper's robust lines in two different bands; if the results disagree by more than the internal scatter, or if a line accepted as robust gives an abundance offset larger than the stated NLTE corrections (about 0.2 dex) when compared against an independent reference, the claim of cross-band and cross-stellar robustness is refuted.
If this is right
- NIR abundance analyses can adopt the tabulated lines as a library of reliable diagnostics across spectral types from F dwarfs to M giants.
- The quantitative framework can be re-executed automatically as new laboratory atomic data, atmosphere models, or instruments become available.
- The approach provides a way to detect problematic lines without empirical recalibration, isolating the atomic data or model as the source of disagreement.
- The result that only Sr II among n-capture elements passes the tests implies that systematic searches for heavier-element lines in the NIR need further work.
- The line list can serve as a cross-check for survey pipelines that rely on astrophysically calibrated lists.
Where Pith is reading between the lines
- Applying the same four-stage filter to other spectral bands (e.g., K or L bands) or to a larger sample of benchmark stars could extend the validated line library and test the thresholds' generality.
- The purity criterion could be combined with 3D and NLTE synthetic spectra, since the paper itself notes IR NLTE corrections up to 0.2 dex; such tests might revise which lines survive.
- The reproducibility of the pipeline means a community-driven effort could maintain a living line list, updating flags whenever atomic data are revised.
- For elements lacking optical abundances, the practice of scaling to metallicity is a clear limitation; a dedicated star with independently determined abundances for those elements would make a sharper test.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper presents a quantitative, multi-criteria pipeline for selecting robust atomic absorption lines in the near-infrared Y, J, and H bands (9800–18000 Å) for abundance analyses of FGK stars. Six Gaia FGK Benchmark Stars observed with CRIRES+ are analyzed using 1D-LTE MARCS/MOOG synthetic spectra computed from VALD3 laboratory atomic data and benchmark stellar parameters. Each candidate transition is evaluated for line depth, saturation, purity (blending), and goodness of fit against observed profiles. Lines that pass all four criteria in a given band are labeled YYYY and compiled as 'robust' lists per spectral type in Appendices A.1–A.6, with input–output counts summarized in Table B.1. The robust lists are cross-matched against APOGEE, Şentürk et al. (2024), and Marfil et al. (2020), showing partial overlap. The paper claims to provide a reproducible, laboratory-grounded line list useful across a wide range of stellar parameters.
Significance. If the reported lists were internally consistent, the paper would offer a valuable community resource: a homogeneous NIR line selection based on a transparent, deterministic decision tree, with genuinely external validation through cross-matching (33 transitions in common with APOGEE for the Sun, 24 for Arcturus, 22 with Şentürk, and 15 Fe I with Marfil). The pipeline is described in sufficient detail to be rerun as atomic data improve, and the authors explicitly recognize several modeling limitations (LTE-only synthesis, missing molecular data for the coolest star, approximate abundance scaling). However, the central data product is compromised as printed: the robust line lists in Appendices A.1–A.6 and the summary counts in Table B.1 contradict each other by large factors for many spectral classes and bands. A user cannot determine which transitions are actually recommended. In addition, the GoF step tests consistency with abundance assumptions that are not independently constrained for alpha-elements in metal-poor stars. These issues are load-bearing for the paper's main claim, though they appear fixable by re-running the pipeline and performing targeted sensitivity tests.
major comments (4)
- [Appendix A vs Appendix B, Table B.1] The manuscript states that Table B.1 reports 'the number of transitions that pass all selection criteria' (i.e., final YYYY outcomes), so its numbers must match the contents of Appendices A.1–A.6. They do not. For example, H-band M giant: Appendix A.6 lists 8 Fe I, 5 Si I, and 1 V I, while Table B.1 gives Fe I=0, Si I=1, and no V I row. G-dwarf H: Appendix A.2 lists 16 Fe I and 9 Si I, but Table B.1 gives Fe I=4 and Si I=16. F-dwarf H: Appendix A.1 lists 4 Si I, but Table B.1 gives 6. J-band M giant: Appendix A.6 lists 7 Fe I, 10 Si I, 3 Cr I, and 7 Ti I, but Table B.1 gives 4, 8, 0, and 5. These are not minor typos in a wavelength entry; the two published summaries of the central deliverable are systematically inconsistent. As printed, the robust list is not reproducible, and the main claim is unsupported. The authors must reconcile these tables, explain the discrepancy (e.g., counting
- [Sections 3.1 and 3.2.4, Table 2] The GoF stage evaluates how well a synthesis matches the observed spectrum, but the synthesis uses [X/H] scaled to the star's global [M/H] for elements without individual optical abundances, including Si. For Arcturus ([Fe/H]=−0.55, [α/Fe]∼+0.3), this sets [Si/H]≈−0.55 instead of the likely ≈−0.25. The synthetic Si lines are then too weak, and the GoF may reject a perfectly good Si line because the input abundance is wrong, or accept a line only because the abundance error compensates for atomic-data error. Since the paper's cross-match counts and robust lists emphasize Si I lines, this assumption is load-bearing for the alpha-element conclusions. Please run a sensitivity test: redo the Si I selection for Arcturus with [Si/H] from the literature (or with [Si/Fe]=+0.3) and report whether the YYYY decisions change. If they do, the claim of robustness across the full stellar-parameter range
- [Section 3.2.1, Eq. (1), Table 1] The depth threshold is d≥0.03, and the paper states that for S/N∼100, Eq. (1) gives σ≈0.01, so d=0.03 is a ∼3σ detection. However, the H-band spectrum of γ Sge has S/N=37.8 (Table 1), for which σ=1/37.8≈0.026 and d=0.03 is only a ∼1.2σ feature. The M-giant H-band robust list (Appendix A.6) is therefore potentially dominated by noise fluctuations. The selection should either mask this low-S/N band/class, apply an S/N-dependent depth threshold, or provide a quantitative justification for why the fixed 0.03 threshold remains reliable at S/N≈38. Without this, the H-band M-giant conclusions are not supported.
- [Sections 3.1 and 3.2.1] The entire selection is based on 1D-LTE synthesis, while the paper itself cites NLTE abundance corrections up to 0.2 dex for IR lines of Si I and Ca II (Section 3.2.1). A line that passes the GoF in LTE may fail when NLTE effects are included, and vice versa. Although the authors frame this as a framework that can be updated, the central claim is that the selected lines are 'robust' for abundance work. The paper should quantify how many of the final YYYY lines have known NLTE corrections exceeding, say, 0.1 dex, and whether any of the rejected lines would be recovered under NLTE. This is a concrete, testable addition that would materially strengthen the robustness claim.
minor comments (4)
- [Section 4] The cross-match paragraph states 33 transitions in common with APOGEE for the G dwarf, but the breakdown (12 Fe I + 9 Si I + 4 Mg I + 3 N I + 3 C I + 1 Si + 1 Cr I + 1 K I) sums to 34. Please check the count.
- [Section 3.2.2] In the text describing saturation, 'a line is flagged as Unsaturated N when...' should presumably read 'flagged as saturated' (the N flag indicates saturation). The placeholder 'element_id' in the same section is unresolved.
- [Appendix A.2, H band] In the G-dwarf H-band list, 'Si15400.077' appears adjacent to 'Sii...' lines; please clarify whether this is Si I (neutral) or a separate species, and ensure consistent notation throughout the appendices.
- [Section 2] The nominal resolution is reported as 'R∼90000' in the introduction and '∼100000' in Section 2; Table 2 and the synthesis use R=90000. Please harmonize the values or explain the difference.
Circularity Check
No significant circularity: robust-line selection is conditional on external benchmark parameters and is not used to fit the abundances entering the synthesis.
full rationale
The paper's central claim is a line-selection result, not a derivation that folds its conclusion back into its inputs. The synthesis uses stellar parameters from Soubiran et al. (2024) and optical abundances from Casamiquela et al. (2025), both external to the IR line list being vetted; Teff/logg rest on interferometric diameters, bolometric fluxes, and parallaxes, and the abundance inputs come from a different wavelength regime. The four filtering stages (depth, saturation, purity, GoF) apply fixed, a priori thresholds: no threshold is tuned line-by-line to force acceptance, and the accepted lines are never used to recompute the abundances that enter the synthesis. Purity is a synthetic-spectrum property of each candidate, not a quantity derived from the final list. The cross-matches against APOGEE, Şentürk et al., and Marfil et al. are independent external checks, not inputs. The paper honestly discloses model-dependence limitations (LTE assumptions, molecular contamination for γSge, up to 0.2 dex NLTE corrections cited for Si I and Ca II), but those are accuracy risks rather than circular steps. The apparent inconsistency between Appendix A robust-line lists and Table B.1 counts is a reproducibility/correctness issue, not a circularity issue, and therefore does not affect this score.
Axiom & Free-Parameter Ledger
free parameters (5)
- Line depth threshold =
d = 0.03
- Saturation slope and core-flux thresholds =
COG local slope < 0.5 and dF_core < 0.005
- Purity acceptance thresholds =
P<0.5 reject; 0.5-0.75 undecided; P>=0.75 accept
- Per-band GoF thresholds =
Y: RMSE 0.035, MAD 0.02; J: 0.038, 0.024; H: 0.05, 0.05; plus 10% chi-square relaxation
- Abundance scaling for unmeasured species =
[X/H] = [M/H] (global metallicity)
axioms (5)
- domain assumption 1D LTE MARCS models describe NIR line formation faithfully enough for the filters
- domain assumption VALD3 (version 968) laboratory line data are complete and accurate in the Y, J, and H bands
- domain assumption GBS benchmark parameters (Soubiran et al. 2024) and optical abundances (Casamiquela et al. 2025) are correct
- domain assumption Residual telluric contamination below 5% after MOLECFIT correction does not bias GoF and purity metrics
- standard math Depth, curve-of-growth, and purity criteria jointly diagnose line suitability
read the original abstract
The advent of new and more powerful infrared spectrographs has significantly motivated the advancement of the study of atomic and molecular line lists and stellar atmosphere models. While optical abundance determinations rely on extensively validated line lists and modeling frameworks, infrared measurements still face larger uncertainties, largely driven by the choice of atmospheric models and the quality of the available atomic data. In this work, we aim to deliver a homogeneous and reproducible set of atomic absorption lines in the Y, J, and H bands (9800 - 18000 (Angstrom)), based exclusively on laboratory atomic data. We analyse CRIRES spectra of six Gaia FGK Benchmark Stars spanning a wide range in effective temperature, surface gravity, and chemical composition. Synthetic spectra are computed using the benchmark stellar parameters, and each transition is evaluated independently in every star through a quantitative sequence that examines line depth, saturation, blending (purity), and the agreement between observed and synthetic line profiles. We identify a set of robust atomic transitions in these bands that remain consistent across the full range of stellar parameters represented in our sample. Lines of alpha-elements such as Mg I, Si I, and Ca I, together with several Fe I transitions, satisfy all robustness criteria. Among the neutron-capture species explored, only Sr II provides lines that consistently meet our requirements. Beyond the specific list of accepted transitions, this study demonstrates that a fully quantitative, multi-criteria framework provides a transparent and reproducible foundation for near-infrared line validation as laboratory data, stellar atmosphere models, and instrumentation continue to improve.
Figures
Reference graph
Works this paper leans on
-
[1]
2016, ApJ, 819, 103
Afşar, M., Sneden, C., Frebel, A., et al. 2016, ApJ, 819, 103
2016
-
[2]
M., Lind, K., Asplund, M., Barklem, P
Amarsi, A. M., Lind, K., Asplund, M., Barklem, P. S., & Collet, R. 2016, MNRAS, 463, 1518
2016
-
[3]
M., Lind, K., Osorio, Y., et al
Amarsi, A. M., Lind, K., Osorio, Y., et al. 2020, A&A, 642, A62
2020
-
[4]
M., et al
Bergemann, M., Collet, R., Amarsi, A. M., et al. 2017, ApJ, 847, 15
2017
-
[5]
2012, ApJ, 751, 156
Bergemann, M., Kudritzki, R.-P., Plez, B., et al. 2012, ApJ, 751, 156
2012
-
[6]
2014, A&A, 569, A111
Blanco-Cuaresma, S., Soubiran, C., Heiter, U., & Jofré, P. 2014, A&A, 569, A111
2014
-
[7]
L., Rix, H.-W., et al
Bovy, J., Nidever, D. L., Rix, H.-W., et al. 2014, ApJ, 790, 127
2014
-
[8]
2005, A&A, 441, 533
Caffau, E., Bonifacio, P., Faraggiana, R., et al. 2005, A&A, 441, 533
2005
-
[9]
2025, arXiv e-prints, arXiv:2504.19648
Casamiquela, L., Soubiran, C., Jofré, P., et al. 2025, arXiv e-prints, arXiv:2504.19648
arXiv 2025
-
[10]
2014, in Society of Photo- Optical Instrumentation Engineers (SPIE) Conference Series, Vol
Cirasuolo, M., Afonso, J., Carollo, M., et al. 2014, in Society of Photo- Optical Instrumentation Engineers (SPIE) Conference Series, Vol. 9147, Ground-based and Airborne Instrumentation for Astronomy V, ed. S. K. Ramsay, I. S. McLean, & H. Takami, 91470N Şentürk, S. A., Şahin, T., Güney, F., Bilir, S., & Marışmak, M. 2024, ApJ, 976, 175
2014
-
[11]
J., Bristow, P., Smoker, J
Dorn, R. J., Bristow, P., Smoker, J. V., et al. 2023, A&A, 671, A24
2023
-
[12]
S., Matsunaga, N., Jian, M., et al
Elgueta, S. S., Matsunaga, N., Jian, M., et al. 2024, MNRAS, 532, 3694
2024
-
[13]
M., et al
Freudling, W., Romaniello, M., Bramich, D. M., et al. 2013, A&A, 559, A96 García Pérez, A. E., Allende Prieto, C., Holtzman, J. A., et al. 2016, AJ, 151, 144
2013
-
[14]
P., Mather, J
Gardner, J. P., Mather, J. C., Abbott, R., et al. 2023, Publications of the Astronomical Society of the Pacific, 135, 068001
2023
-
[15]
E., Rothman, L
Gordon, I. E., Rothman, L. S., Hargreaves, R. J., et al. 2022, J. Quant. Spectr. Rad. Transf., 277, 107949
2022
-
[16]
Gray, D. F. 2005, The Observation and Analysis of Stellar Photo- spheres, 3rd edn. (Cambridge University Press)
2005
-
[17]
2014, AJ, 148, 53
Gullikson, K., Dodson-Robinson, S., & Kraus, A. 2014, AJ, 148, 53
2014
-
[18]
2008, A&A, 486, 951
Gustafsson, B., Edvardsson, B., Eriksson, K., et al. 2008, A&A, 486, 951
2008
-
[19]
D., et al
Hahlin, A., Kochukhov, O., Rains, A. D., et al. 2023, A&A, 675, A91
2023
-
[20]
2016, A&A, 592, A70
Hawkins, K., Jofré, P., Heiter, U., et al. 2016, A&A, 592, A70
2016
-
[21]
R., Bovy, J., Holtzman, J
Hayden, M. R., Bovy, J., Holtzman, J. A., et al. 2015, ApJ, 808, 132
2015
-
[22]
2015, A&A, 582, A49
Heiter, U., Jofré, P., Gustafsson, B., et al. 2015, A&A, 582, A49
2015
-
[23]
2021, A&A, 645, A106 Jofré, P., Heiter, U., & Soubiran, C
Heiter, U., Lind, K., Bergemann, M., et al. 2021, A&A, 645, A106 Jofré, P., Heiter, U., & Soubiran, C. 2019, ARA&A, 57, 571 Jofré, P., Heiter, U., Soubiran, C., et al. 2015, A&A, 582, A81 Jofré, P., Heiter, U., Soubiran, C., et al. 2014, A&A, 564, A133 Kaeufl,H.-U.,Ballester,P.,Biereichel,P.,etal.2004,inGround-based Instrumentation for Astronomy, ed. A. F...
2021
-
[24]
2019, ApJ, 875, 129
Kondo, S., Fukue, K., Matsunaga, N., et al. 2019, ApJ, 875, 129
2019
-
[25]
2012, MNRAS, 427, 50
Lind, K., Bergemann, M., & Asplund, M. 2012, MNRAS, 427, 50
2012
-
[26]
1984, Astronomy and Astrophysics, 134, 189
Magain, P. 1984, Astronomy and Astrophysics, 134, 189
1984
-
[27]
H., & Rieke, M
Maiolino, R., Rieke, G. H., & Rieke, M. J. 1996, AJ, 111, 537
1996
-
[28]
R., Schiavon, R
Majewski, S. R., Schiavon, R. P., Frinchaboy, P. M., et al. 2017, AJ, 154, 94
2017
-
[29]
M., Montes, D., et al
Marfil, E., Tabernero, H. M., Montes, D., et al. 2020, MNRAS, 492, 5470
2020
-
[30]
R., Korn, A
Mashonkina, L., Gehren, T., Shi, J. R., Korn, A. J., & Grupp, F. 2011, A&A, 528, A87
2011
-
[31]
2020, ApJS, 246, 10
Matsunaga, N., Taniguchi, D., Jian, M., et al. 2020, ApJS, 246, 10
2020
-
[32]
1978, Stellar Atmospheres, 2nd edn
Mihalas, D. 1978, Stellar Atmospheres, 2nd edn. (San Francisco: W. H. Freeman and Company)
1978
-
[33]
E., Akerman, C., Asplund, M., et al
Nissen, P. E., Akerman, C., Asplund, M., et al. 2007, A&A, 469, 319
2007
-
[34]
2012, A&A, 543, A92
Noll, S., Kausch, W., Barden, M., et al. 2012, A&A, 543, A92
2012
-
[35]
2020, A&A, 637, A80
Osorio, Y., Allende Prieto, C., Hubeny, I., Mészáros, S., & Shetrone, M. 2020, A&A, 637, A80
2020
-
[36]
Queiroz, A. B. A., Anders, F., Chiappini, C., et al. 2020, A&A, 638, A76
2020
-
[37]
L., et al
Ryabchikova, T., Piskunov, N., Kurucz, R. L., et al. 2015, Phys. Scr, 90, 054005
2015
-
[38]
2009, A&A, 496, 701
Ryde, N., Edvardsson, B., Gustafsson, B., et al. 2009, A&A, 496, 701
2009
-
[39]
Ryde, N., Edvardsson, B., Gustafsson, B., & Käufl, H. U. 2007, in IAU Symposium, Vol. 241, Stellar Populations as Building Blocks of Galaxies, ed. A. Vazdekis & R. Peletier, 260–261
2007
-
[40]
2010, A&A, 509, A20
Ryde, N., Gustafsson, B., Edvardsson, B., et al. 2010, A&A, 509, A20
2010
-
[41]
2019, A&A, 631, L3
Ryde, N., Hartman, H., Oliva, E., et al. 2019, A&A, 631, L3
2019
-
[42]
2018, PASP, 130, 074502
Sameshima, H., Matsunaga, N., Kobayashi, N., et al. 2018, PASP, 130, 074502
2018
-
[43]
2010, AJ, 139, 646
Sharon, C., Hillenbrand, L., Fischer, W., & Edwards, S. 2010, AJ, 139, 646
2010
-
[44]
E., et al
Shetrone, M., Bizyaev, D., Lawler, J. E., et al. 2015, ApJS, 221, 24
2015
-
[45]
2015, ApJ, 808, 148
Sitnova, T., Zhao, G., Mashonkina, L., et al. 2015, ApJ, 808, 148
2015
-
[46]
2015, A&A, 576, A77
Smette, A., Sana, H., Noll, S., et al. 2015, A&A, 576, A77
2015
-
[47]
V., Bizyaev, D., Cunha, K., et al
Smith, V. V., Bizyaev, D., Cunha, K., et al. 2021, AJ, 161, 254
2021
-
[48]
2012, MOOG: LTE line analysis and spectrum synthesis
Sneden, C., Bean, J., Ivans, I., Lucatello, S., & Sobeck, J. 2012, MOOG: LTE line analysis and spectrum synthesis
2012
-
[49]
L., Lagarde, N., et al
Soubiran, C., Creevey, O. L., Lagarde, N., et al. 2024, A&A, 682, A145
2024
-
[50]
M., et al
Spite, M., Caffau, E., Andrievsky, S. M., et al. 2011, A&A, 528, A9
2011
-
[51]
M., et al
Thorsbro, B., Ryde, N., Rich, R. M., et al. 2020, ApJ, 894, 26
2020
-
[52]
J., Santos, N
Ulmer-Moll, S., Figueira, P., Neal, J. J., Santos, N. C., & Bonnefoy, M. 2019, A&A, 621, A79
2019
-
[53]
D., Cushing, M
Vacca, W. D., Cushing, M. C., & Rayner, J. T. 2003, PASP, 115, 389
2003
-
[54]
2016, ApJ, 833, 137 Article number, page 15 of 22 A&A proofs:manuscript no
Zhang, J., Shi, J., Pan, K., Allende Prieto, C., & Liu, C. 2016, ApJ, 833, 137 Article number, page 15 of 22 A&A proofs:manuscript no. aanda Appendix A: Robust lines A.1. F Dwarf Table A.1.Robust (YYYY) transitions for F Dwarf in the Y, J, and H bands. Y band (F Dwarf) – 18 lines Ci10123.870, 10541.240, 10729.530 Fei9944.207 Ni10112.481, 10114.640 Nii9898...
2016
discussion (0)
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