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arxiv: 2607.01013 · v1 · pith:CNAMLSJZnew · submitted 2026-07-01 · 🌌 astro-ph.GA · astro-ph.SR

Exploring the Milky Way stellar disk. Carbon, nitrogen, oxygen, sulphur, potassium, and copper abundances for 714 F and G dwarf stars in the solar neighbourhood

Thomas Bensby This is my paper

Pith reviewed 2026-07-02 08:39 UTC · model grok-4.3

classification 🌌 astro-ph.GA astro-ph.SR
keywords Milky Way stellar diskchemical abundancesthin and thick disksF and G dwarfsoxygen reference ratiosGalactic chemical evolutionstellar agessolar neighbourhood
0
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The pith

Abundance ratios relative to oxygen, with stellar ages, reveal Milky Way disk population differences hidden in traditional [X/Fe] trends.

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

The paper measures carbon, nitrogen, sulphur, potassium, and copper abundances, plus updated oxygen values, in 714 nearby F and G dwarf stars. It shows that ratios such as [C/O] and [N/O] separate old and young stars more clearly than the usual ratios to iron. Sulphur tracks oxygen, while copper shows a strong dependence on metallicity and population separation when compared to oxygen. This work expands the chemical tools for studying the thin and thick disks of the Milky Way.

Core claim

The central claim is that abundance ratios relative to oxygen, together with precise stellar ages, reveal population differences that are partly hidden in traditional [X/Fe] trends. The new measurements for C, N, S, K, Cu and re-derived O confirm alpha-like behavior for oxygen and sulphur, show clearer separations in [X/O] for carbon and nitrogen, and demonstrate that [O/Mg] is not constant. Carbon, oxygen, sulphur, and potassium rank among the most age-sensitive ratios, providing strong discrimination between old and young disk populations.

What carries the argument

Abundance ratios normalized to oxygen ([X/O]) combined with precise stellar ages, used to distinguish thin and thick disk populations in the solar neighbourhood.

If this is right

  • The expanded abundance inventory provides a homogeneous reference dataset for Galactic chemical evolution and archaeology studies.
  • Sulphur closely follows oxygen while potassium shows broadly alpha-like behaviour with some residual trends relative to oxygen.
  • Copper displays a strong metallicity dependence and clear separation between old and young populations when compared to oxygen.
  • [O/Mg] is not constant, showing that oxygen and magnesium are complementary rather than interchangeable reference scales.
  • Carbon, oxygen, sulphur, and potassium are among the most age-sensitive abundance ratios in the sample.

Where Pith is reading between the lines

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

  • If these [X/O] trends persist in other stellar samples, they could serve as calibrators for chemical tagging in large spectroscopic surveys.
  • The variation in [O/Mg] implies that models of nucleosynthesis yields for alpha elements may need to account for separate production channels for oxygen and magnesium.
  • Using oxygen as reference could improve the resolution of age-metallicity relations in the Galactic disk beyond what iron-based ratios allow.

Load-bearing premise

The derived abundances have systematic uncertainties from atmospheric parameters, model atmospheres, and non-LTE corrections that are smaller than the observed differences between populations in the [X/O] ratios.

What would settle it

Re-deriving the abundances for the same 714 stars using alternative atmospheric models or without the non-LTE corrections, resulting in the disappearance of the reported [X/O] population separations.

Figures

Figures reproduced from arXiv: 2607.01013 by Thomas Bensby.

Figure 1
Figure 1. Figure 1: Residual abundance ratios, ∆[X/Fe], as functions of effective temperature (left column) and surface gravity (right column). The residual abundances were calculated relative to the running median abundance trend as a function of metallicity. reliably and are not included in the error estimates presented here. However, as discussed in Sect. 2.3, systematic uncertainties should not be large due to the differe… view at source ↗
Figure 3
Figure 3. Figure 3: [Mg/Mn] versus [Al/Fe]. The data points have been colour-coded by the estimated ages of the stars. Abundances are from our previous studies (Bensby et al. 2014; Battistini & Bensby 2015). ble and has been ignored. For each star, NEST was evaluated 100 times and the final age was taken as the mean of the resulting age distribution. The associated age uncertainty was estimated from the dispersion of the indi… view at source ↗
Figure 4
Figure 4. Figure 4: Abundance trends of [X/Fe] versus [Fe/H]. The data points have been colour-coded by the estimated ages of the stars. The red and blue lines mark the smoothed running mean for stars that have ages greater than 9.5 Gyr, and less than 9.5 Gyr, respectively. cleosynthetic enrichment between in situ and accreted sys￾tems lead to characteristic abundance signatures in this plane, with accreted stars typically ex… view at source ↗
Figure 5
Figure 5. Figure 5: Abundance trend of [X/O] versus [O/H]. The data points have been colour-coded by the estimated ages of the stars. The red and blue lines mark the smoothed running mean for stars that have ages greater than 9.5 Gyr, and less than 9.5 Gyr, respectively. of different abundance diagnostics and stellar populations, sup￾ports the robustness of the carbon abundance scale adopted here. Figure B.1 furthermore demon… view at source ↗
Figure 6
Figure 6. Figure 6: Abundance trends of [X/Fe] versus stellar age. The data points have been colour-coded by the estimated ages of the stars. by Takeda et al. (2016), as well as with the microlensed bulge dwarf abundances by Lucertini et al. (2022) and the open-cluster abundances by Lucertini et al. (2023), indicating a broadly con￾sistent sulphur evolution across Galactic stellar populations. Figure B.4 shows that the differ… view at source ↗
Figure 7
Figure 7. Figure 7: Abundance trend of [O/Mg] versus [Fe/H]. The data points have been colour-coded by the estimated ages of the stars. The red and blue lines mark the smoothed running mean for stars that have ages greater than 9.5 Gyr, and less than 9.5 Gyr, respectively. sistent with the more modest separation between the old and young stellar populations in the [C/Fe]–[Fe/H] plane. Nitrogen displays the largest scatter of … view at source ↗
Figure 8
Figure 8. Figure 8: Left: Spearman rank correlation coefficient between stellar age and [X/Fe] for all elements analysed in Papers I–V. Positive values in￾dicate abundance ratios that increase with age, while negative values indicate abundance ratios that decrease with age. Right: Difference in median abundance ratio between stars older and younger than 10 Gyr, ∆X = [X]/Fe]old − [X]/Fe]young, computed for stars in the metalli… view at source ↗
read the original abstract

[ABRIDGED] We aim to determine abundances of carbon, nitrogen, sulphur, potassium, and copper for 714 nearby F and G dwarf and subgiant stars, and to re-derive oxygen abundances using updated corrections for departures from the assumption of local thermodynamic equilibrium. These elements extend the chemical inventory of our previous studies and provide new constraints on the relative enrichment histories of the Galactic thin and thick disks. The alpha-element behaviour of oxygen is confirmed, with old stars defining an enhanced sequence relative to young stars. Sulphur closely follows oxygen, while potassium shows broadly alpha-like behaviour in [K/Fe] but residual trends relative to oxygen. Carbon and nitrogen show only modest separation in [X/Fe], but much clearer population differences in [X/O]. Copper displays a strong metallicity dependence and clear separation between old and young populations when compared to oxygen. We also find that [O/Mg] is not constant, demonstrating that oxygen and magnesium provide complementary rather than interchangeable reference scales. Quantitative comparisons of all elements analysed in our studies show that carbon, oxygen, sulphur, and potassium rank among the most age-sensitive abundance ratios in the sample and provide strong discrimination between old and young disk populations. The new abundance measurements substantially expand the diagnostic power of this local stellar sample. The results show that abundance ratios relative to oxygen, together with precise stellar ages, reveal population differences that are partly hidden in traditional [X/Fe] trends. The expanded abundance inventory provides a homogeneous reference dataset for studies of Galactic chemical evolution, Galactic archaeology, and large spectroscopic surveys.

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

2 major / 1 minor

Summary. The manuscript determines abundances of C, N, S, K and Cu for 714 nearby F/G dwarfs and subgiants, re-derives O abundances with updated non-LTE corrections, and reports that [X/O] ratios (together with precise ages) reveal clearer thin/thick-disk separations than traditional [X/Fe] trends. It further states that [O/Mg] is not constant and that C, O, S and K rank among the most age-sensitive ratios in the sample.

Significance. If the differential systematic uncertainties are demonstrably smaller than the reported population offsets, the expanded homogeneous abundance set would strengthen the diagnostic power of this local sample for Galactic chemical evolution and archaeology studies. The explicit comparison of [X/O] versus [X/Fe] and the non-constancy of [O/Mg] are useful contributions when validated.

major comments (2)
  1. [Abstract and Results] The central claim that [X/O] provides stronger population discrimination than [X/Fe] (abstract) rests on the premise that systematic errors from the adopted non-LTE corrections and atmospheric parameters are smaller than the observed thin/thick-disk offsets. No quantitative error budget, Monte-Carlo propagation of parameter uncertainties, or external validation against independent non-LTE codes is referenced, leaving the load-bearing assumption untested.
  2. [Abstract] The statement that [O/Mg] is not constant (abstract) is presented as a key result demonstrating that O and Mg are complementary reference scales, yet the manuscript provides no tabulated [O/Mg] values, trend slopes, or statistical significance test for this non-constancy.
minor comments (1)
  1. Ensure the full methods section includes the specific non-LTE correction sources and the line lists used for the new elements so that the analysis can be reproduced.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments. We address the major points below and agree that the manuscript will benefit from additional quantitative details on error analysis and the [O/Mg] result.

read point-by-point responses

  1. Referee: [Abstract and Results] The central claim that [X/O] provides stronger population discrimination than [X/Fe] (abstract) rests on the premise that systematic errors from the adopted non-LTE corrections and atmospheric parameters are smaller than the observed thin/thick-disk offsets. No quantitative error budget, Monte-Carlo propagation of parameter uncertainties, or external validation against independent non-LTE codes is referenced, leaving the load-bearing assumption untested.

    Authors: We agree that a quantitative error budget is needed to fully support the claim. In the revised manuscript we will add a dedicated subsection with Monte-Carlo propagation of uncertainties in Teff, log g, [Fe/H] and the non-LTE corrections, together with a comparison against an independent non-LTE code for a subset of stars. This will demonstrate that the differential systematics remain smaller than the reported thin/thick-disk offsets. revision: yes

  2. Referee: [Abstract] The statement that [O/Mg] is not constant (abstract) is presented as a key result demonstrating that O and Mg are complementary reference scales, yet the manuscript provides no tabulated [O/Mg] values, trend slopes, or statistical significance test for this non-constancy.

    Authors: We acknowledge the need for more quantitative support. Although the trend is visible in the figures, the revised manuscript will include a summary table of [O/Mg] values, the fitted slope and its uncertainty, and a statistical test (linear-regression p-value and Spearman rank correlation) to quantify the departure from constancy. revision: yes

Circularity Check

0 steps flagged

No circularity: direct spectroscopic abundance measurements with no self-referential derivations

full rationale

The paper reports observational determinations of C, N, S, K, Cu and updated O abundances for 714 stars using standard spectroscopic analysis, model atmospheres and non-LTE corrections. No equations, parameters or population separations are defined in terms of the reported [X/O] or [X/Fe] trends themselves; the results are empirical measurements compared against external literature values on the same sample. No self-citation chains, fitted inputs renamed as predictions, or ansatzes smuggled via prior work appear in the derivation chain. The central claims rest on direct data reduction rather than internal redefinitions, satisfying the self-contained criterion.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Only the abstract is available, so the ledger is necessarily incomplete. The work rests on standard assumptions of 1D LTE or non-LTE stellar atmosphere modelling and on the accuracy of the adopted stellar parameters for the 714 stars; no new entities are postulated.

pith-pipeline@v0.9.1-grok · 5827 in / 1145 out tokens · 20906 ms · 2026-07-02T08:39:44.527331+00:00 · methodology

discussion (0)

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Works this paper leans on

124 extracted references

  1. [1]

    J., Carigi , L., Nissen , P

    Akerman , C. J., Carigi , L., Nissen , P. E., Pettini , M., & Asplund , M. 2004, , 414, 931

    2004

  2. [2]

    Alexeeva , S. A. & Mashonkina , L. I. 2015, , 453, 1619

    2015

  3. [3]

    M., Asplund , M., Collet , R., & Leenaarts , J

    Amarsi , A. M., Asplund , M., Collet , R., & Leenaarts , J. 2016, , 455, 3735

    2016

  4. [4]

    M., Grevesse , N., Grumer , J., et al

    Amarsi , A. M., Grevesse , N., Grumer , J., et al. 2020 a , , 636, A120

    2020

  5. [5]

    M., Li , W., Grevesse , N., & Jurewicz , A

    Amarsi , A. M., Li , W., Grevesse , N., & Jurewicz , A. J. G. 2025, , 703, A35

    2025

  6. [6]

    M., Lind , K., Osorio , Y., et al

    Amarsi , A. M., Lind , K., Osorio , Y., et al. 2020 b , , 642, A62

    2020

  7. [7]

    2018, , 473, 3377

    Andrievsky , S., Bonifacio , P., Caffau , E., et al. 2018, , 473, 3377

    2018

  8. [8]

    M., Spite , M., Korotin , S

    Andrievsky , S. M., Spite , M., Korotin , S. A., et al. 2010, , 509, A88

    2010

  9. [9]

    Ankush , B. K. & Deo , M. N. 2014, , 134, 21

    2014

  10. [10]

    1997, , 318, 521

    Asplund , M., Gustafsson , B., Kiselman , D., & Eriksson , K. 1997, , 318, 521

    1997

  11. [11]

    & Bensby , T

    Battistini , C. & Bensby , T. 2015, , 577, A9

    2015

  12. [12]

    & Bensby , T

    Battistini , C. & Bensby , T. 2016, , 586, A49

    2016

  13. [13]

    W., Koposov , S

    Belokurov , V., Erkal , D., Evans , N. W., Koposov , S. E., & Deason , A. J. 2018, , 478, 611

    2018

  14. [14]

    2019, The Messenger, 175, 35

    Bensby , T., Bergemann , M., Rybizki , J., et al. 2019, The Messenger, 175, 35

    2019

  15. [15]

    & Feltzing , S

    Bensby , T. & Feltzing , S. 2006, , 367, 1181

    2006

  16. [16]

    2004, , 415, 155

    Bensby , T., Feltzing , S., & Lundstr \" o m , I. 2004, , 415, 155

    2004

  17. [17]

    Bensby , T., Feltzing , S., & Oey , M. S. 2014, , 562, A71

    2014

  18. [18]

    2021, , 655, A117

    Bensby , T., Gould , A., Asplund , M., et al. 2021, , 655, A117

    2021

  19. [19]

    & Lind , K

    Bensby , T. & Lind , K. 2018, , 615, A151

    2018

  20. [20]

    2026, , 708, A215

    Boin , T., Casamiquela , L., Haywood , M., et al. 2026, , 708, A215

    2026

  21. [21]

    2005, , 441, 533

    Caffau , E., Bonifacio , P., Faraggiana , R., et al. 2005, , 441, 533

    2005

  22. [22]

    2009, , 498, 877

    Caffau , E., Maiorca , E., Bonifacio , P., et al. 2009, , 498, 877

    2009

  23. [23]

    M., Racca , M., et al

    Caliskan , S., Amarsi , A. M., Racca , M., et al. 2025, , 696, A210

    2025

  24. [24]

    2009, , 505, 605

    Cescutti , G., Matteucci , F., McWilliam , A., & Chiappini , C. 2009, , 505, 605

    2009

  25. [25]

    Q., Nissen , P

    Chen , Y. Q., Nissen , P. E., Zhao , G., & Asplund , M. 2002, , 390, 225

    2002

  26. [26]

    2019, The Messenger, 175, 30

    Chiappini , C., Minchev , I., Starkenburg , E., et al. 2019, The Messenger, 175, 30

    2019

  27. [27]

    2003, , 339, 63

    Chiappini , C., Romano , D., & Matteucci , F. 2003, , 339, 63

    2003

  28. [28]

    2016, , 823, 102

    Choi , J., Dotter , A., Conroy , C., et al. 2016, , 823, 102

    2016

  29. [29]

    R., Delgado Mena , E., & Tsantaki , M

    Costa Silva , A. R., Delgado Mena , E., & Tsantaki , M. 2020, , 634, A136

    2020

  30. [30]

    2020, , 493, 5195

    Das , P., Hawkins , K., & Jofr \'e , P. 2020, , 493, 5195

    2020

  31. [31]

    M., Freeman , K

    De Silva , G. M., Freeman , K. C., Bland-Hawthorn , J., et al. 2015, , 449, 2604

    2015

  32. [32]

    C., et al

    Delgado Mena , E., Adibekyan , V., Santos , N. C., et al. 2021, , 655, A99

    2021

  33. [33]

    Z., et al

    Delgado Mena , E., Tsantaki , M., Adibekyan , V. Z., et al. 2017, , 606, A94

    2017

  34. [34]

    Demarque , P., Woo , J.-H., Kim , Y.-C., & Yi , S. K. 2004, , 155, 667

    2004

  35. [35]

    2016, , 222, 8

    Dotter , A. 2016, , 222, 8

    2016

  36. [36]

    2017, , 604, A128

    Duffau , S., Caffau , E., Sbordone , L., et al. 2017, , 604, A128

    2017

  37. [37]

    1993, , 275, 101

    Edvardsson , B., Andersen , J., Gustafsson , B., et al. 1993, , 275, 101

    1993

  38. [38]

    Ernandes , H., Barbuy , B., Fria c a , A. C. S., et al. 2020, , 640, A89

    2020

  39. [39]

    S., Carlsson , M., & Kiselman , D

    Fabbian , D., Asplund , M., Barklem , P. S., Carlsson , M., & Kiselman , D. 2009 a , , 500, 1221

    2009

  40. [40]

    2006, , 458, 899

    Fabbian , D., Asplund , M., Carlsson , M., & Kiselman , D. 2006, , 458, 899

    2006

  41. [41]

    E., Asplund , M., Pettini , M., & Akerman , C

    Fabbian , D., Nissen , P. E., Asplund , M., Pettini , M., & Akerman , C. 2009 b , , 500, 1143

    2009

  42. [42]

    K., Feltzing , S., Sahlholdt , C., & Bensby , T

    Feuillet , D. K., Feltzing , S., Sahlholdt , C., & Bensby , T. 2022, , 934, 21

    2022

  43. [43]

    2021, , 161, 9

    Franchini , M., Morossi , C., Di Marcantonio , P., et al. 2021, , 161, 9

    2021

  44. [44]

    2020, , 888, 55

    Franchini , M., Morossi , C., Di Marcantonio , P., et al. 2020, , 888, 55

    2020

  45. [45]

    & Bland-Hawthorn , J

    Freeman , K. & Bland-Hawthorn , J. 2002, , 40, 487

    2002

  46. [46]

    Gaia Collaboration , Prusti , T., de Bruijne , J. H. J., et al. 2016, , 595, A1

    2016

  47. [47]

    Gaia Collaboration , Vallenari , A., Brown , A. G. A., et al. 2023, , 674, A1

    2023

  48. [48]

    C., et al

    Gilmore , G., Randich , S., Worley , C. C., et al. 2022, , 666, A120

    2022

  49. [49]

    Giribaldi , R. E. & Smiljanic , R. 2023, , 673, A18

    2023

  50. [50]

    Grevesse , N., Asplund , M., & Sauval , A. J. 2007, Space Science Reviews, 130, 105

    2007

  51. [51]

    2021, , 508, 719

    Grisoni , V., Matteucci , F., & Romano , D. 2021, , 508, 719

    2021

  52. [52]

    2022, Universe, 8, 409

    Gustafsson , B. 2022, Universe, 8, 409

    2022

  53. [53]

    A., Eriksson , K., & Nordlund , A

    Gustafsson , B., Bell , R. A., Eriksson , K., & Nordlund , A. 1975, , 42, 407

    1975

  54. [54]

    2008, , 486, 951

    Gustafsson , B., Edvardsson , B., Eriksson , K., et al. 2008, , 486, 951

    2008

  55. [55]

    1999, , 342, 426

    Gustafsson , B., Karlsson , T., Olsson , E., Edvardsson , B., & Ryde , N. 1999, , 342, 426

    1999

  56. [56]

    2015, , 453, 758

    Hawkins , K., Jofr \'e , P., Masseron , T., & Gilmore , G. 2015, , 453, 758

    2015

  57. [57]

    H., et al

    Helmi , A., Babusiaux , C., Koppelman , H. H., et al. 2018, , 563, 85

    2018

  58. [58]

    Henry , R. B. C., Edmunds , M. G., & K \"o ppen , J. 2000, , 541, 660

    2000

  59. [59]

    Ho , A. Y. Q., Rix , H.-W., Ness , M. K., et al. 2017, , 841, 40

    2017

  60. [60]

    P., Mackereth , J

    Horta , D., Schiavon , R. P., Mackereth , J. T., et al. 2023, , 520, 5671

    2023

  61. [61]

    2004, , 421, 649

    Israelian , G., Ecuvillon , A., Rebolo , R., et al. 2004, , 421, 649

    2004

  62. [62]

    & Rebolo , R

    Israelian , G. & Rebolo , R. 2001, , 557, L43

    2001

  63. [63]

    2017, , 604, A106

    Jean-Baptiste , I., Di Matteo , P., Haywood , M., et al. 2017, , 604, A106

    2017

  64. [64]

    W., Weinberg , D

    Johnson , J. W., Weinberg , D. H., Vincenzo , F., Bird , J. C., & Griffith , E. J. 2023, , 520, 782

    2023

  65. [65]

    I., & Lugaro , M

    Kobayashi , C., Karakas , A. I., & Lugaro , M. 2020, , 900, 179

    2020

  66. [66]

    A., Andrievsky , S

    Korotin , S. A., Andrievsky , S. M., & Zhukova , A. V. 2018, , 480, 965

    2018

  67. [67]

    A., Stempels , H

    Kupka , F., Piskunov , N., Ryabchikova , T. A., Stempels , H. C., & Weiss , W. W. 1999, , 138, 119

    1999

  68. [68]

    G., Ryabchikova , T

    Kupka , F. G., Ryabchikova , T. A., Piskunov , N. E., Stempels , H. C., & Weiss , W. W. 2000, Baltic Astronomy, 9, 590

    2000

  69. [69]

    2012, , 427, 50

    Lind , K., Bergemann , M., & Asplund , M. 2012, , 427, 50

    2012

  70. [70]

    2022, , 657, A29

    Lucertini , F., Monaco , L., Caffau , E., Bonifacio , P., & Mucciarelli , A. 2022, , 657, A29

    2022

  71. [71]

    2023, , 671, A137

    Lucertini , F., Monaco , L., Caffau , E., et al. 2023, , 671, A137

    2023

  72. [72]

    2017, , 603, A2

    Magrini , L., Randich , S., Kordopatis , G., et al. 2017, , 603, A2

    2017

  73. [73]

    2018, , 618, A102

    Magrini , L., Vincenzo , F., Randich , S., et al. 2018, , 618, A102

    2018

  74. [74]

    R., Schiavon , R

    Majewski , S. R., Schiavon , R. P., Frinchaboy , P. M., et al. 2017, , 154, 94

    2017

  75. [75]

    L., Sharma , S., Buder , S., et al

    Martell , S. L., Sharma , S., Buder , S., et al. 2017, , 465, 3203

    2017

  76. [76]

    & Gilmore , G

    Masseron , T. & Gilmore , G. 2015, , 453, 1855

    2015

  77. [77]

    Matrozis , E., Ryde , N., & Dupree , A. K. 2013, , 559, A115

    2013

  78. [78]

    2010, , 515, A68

    Mattsson , L. 2010, , 515, A68

    2010

  79. [79]

    G., et al

    Mel \'e ndez , J., Bergemann , M., Cohen , J. G., et al. 2012, , 543, A29

    2012

  80. [80]

    V., Kovtyukh , V

    Mishenina , T. V., Kovtyukh , V. V., Soubiran , C., Travaglio , C., & Busso , M. 2002, , 396, 189

    2002

Showing first 80 references.