pith. sign in

arxiv: 1906.11458 · v1 · pith:DBSOB7NZnew · submitted 2019-06-27 · 🌌 astro-ph.SR · astro-ph.GA

NGC 6388 reloaded: some like it hot, but not too much

Eugenio Carretta , Angela Bragaglia (INAF-OAS Bologna) This is my paper

Pith reviewed 2026-05-25 14:47 UTC · model grok-4.3

classification 🌌 astro-ph.SR astro-ph.GA
keywords globular clustersmultiple stellar populationsNGC 6388chemical abundancesproton-capture elementsAGB starsmassive starsnucleosynthesis
0
0 comments X

The pith

New diagnostic plots applied to 185 stars constrain the temperature of polluters in NGC 6388 to 100-150 million Kelvin.

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

This paper introduces diagnostic plots called DOHT to detect signatures of proton-capture reactions at very high temperatures. Applied to the largest sample of 185 giant stars with detailed abundances in NGC 6388, the plots allow inference of the central temperature range for the first-generation polluters that shaped the cluster's chemical patterns. If the polluters are massive stars undergoing hydrostatic H-burning, the range is 100 to 150 MK; if massive AGB stars, it narrows to 110-120 MK. A sympathetic reader would care because this provides concrete temperature limits on the sources of the multiple stellar populations observed in globular clusters.

Core claim

Using the new DOHT plots on detailed abundances from 185 stars, the central temperature of part of the polluters must have been between about 100 and 150 million Kelvin if considering hydrostatic H-burning in the core of massive stars. A much narrower range of 110 to 120 MK is inferred if the polluters can be identified in massive asymptotic giant branch stars.

What carries the argument

The DOHT (Detectors Of High Temperature) H-burning plots, new diagnostic diagrams that detect evidence of proton-capture reactions occurring at very high temperatures.

If this is right

  • The polluters in NGC 6388 experienced central temperatures in the 100-150 MK range for massive stars or 110-120 MK for AGB stars.
  • The abundance patterns in the cluster result from high-temperature H-burning in those specific ranges.
  • The method distinguishes between candidate polluter types by the width of the allowed temperature window.
  • Similar temperature constraints can be derived for other globular clusters using the same plots.

Where Pith is reading between the lines

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

  • The DOHT plots could be applied to other massive globular clusters to test whether polluter temperatures are uniform or vary with cluster properties.
  • Confirmation of the narrow temperature window may help prioritize between competing models of early cluster enrichment.
  • Extending the plots to include additional elements might further refine the temperature bounds or reveal mixed contributions from different polluter types.

Load-bearing premise

The observed abundance anticorrelations are produced exclusively by proton-capture nucleosynthesis at the temperatures isolated by the new DOHT plots, with no significant contribution from other processes or dilution effects.

What would settle it

Finding a sample of stars in NGC 6388 whose abundance ratios require proton-capture temperatures outside the 100-150 MK window while still matching the observed anticorrelations would falsify the claimed temperature range.

Figures

Figures reproduced from arXiv: 1906.11458 by Angela Bragaglia (INAF-OAS Bologna), Eugenio Carretta.

Figure 1
Figure 1. Figure 1: Anti-correlation of [Mg/Fe] and [Si/Fe] abundance ratios in NGC 6388. Blue and red circles indicate stars from Paper I and the new stars analyzed in Carretta and Bragaglia (2019a), respectively. The Spearman rank correlation (rS ) coefficient, the Pearson linear correla￾tion (rP) coefficient and its p-value are listed [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: The ratios [Mg/Fe] (184 stars), [Ca/Fe], and [Sc/Fe] (185 stars) from FLAMES spectra in NGC 6388 (Carretta and Bragaglia 2019a) as a function of effective temperature. Internal error bars are shown in each panel. A second limit to the temperature range in FG polluters ac￾tive at the cluster formation may be provided by looking at the abundances of Mg, Ca, and Sc, available for 184, 185, and 185 stars, resp… view at source ↗
Figure 3
Figure 3. Figure 3: The ratios [Ca/H] (left panel) and [Sc/H] (right panel) as a function of [Mg/H] for giants in NGC 6388 (red points), superimposed to field stars from Gratton et al. (2003; blue triangles). Green triangles are giants in NGC 2808 from Carretta (2015). Internal star-to-star errors refer to NGC 6388. Denisenkov, P.A.,& Denisenkova, S.N. 1989, A.Tsir., 1538, 11 Denissenkov, P.A., Hartwick, F.D.A. 2014, MNRAS, 4… view at source ↗
read the original abstract

Multiple stellar populations in globular clusters (GCs) are defined and recognized by their chemical signature, with second generation stars showing the effects of nucleosynthesis in the more massive stars of the earliest component formed in the first star formation burst. High temperature H-burning produces the whole pattern of (anti)-correlations among proton-capture elements widely found in GCs. However, where this burning occurred is still debated. Here we introduce new powerful diagnostic plots to detect evidence (if any) of products from proton-capture reactions occurring at very high temperatures. To test these Detectors Of High Temperature (in short DOHT) H-burning plots we show how to put stringent constraints on the temperature range of the first generation polluters that contributed to shape the chemistry of multiple stellar population in the massive bulge GC NGC 6388. Using the largest sample to date (185 stars) of giants with detailed abundance ratios in a single GC (except omega Cen) we may infer that the central temperature of part of the polluters must have been comprised between about 100 and about 150 million Kelvin (MK) if we consider hydrostatic H-burning in the core of massive stars. A much narrower range (110 to 120 MK) is inferred if the polluters can be identified in massive asymptotic giant branch (AGB) stars.

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 introduces new diagnostic plots (DOHT) based on proton-capture element anticorrelations to constrain the central temperatures of first-generation polluters in the globular cluster NGC 6388. Using abundance data for a sample of 185 giant stars—the largest in a single GC except omega Cen—it infers that the polluters experienced hydrostatic H-burning at central temperatures of 100–150 MK if massive stars or a narrower 110–120 MK if massive AGB stars.

Significance. If the DOHT plots map observed anticorrelations directly to temperature without significant degeneracies, the work would provide a useful new constraint on polluter models for multiple populations in GCs. The large sample size (185 stars) is a clear strength that enables better statistical characterization of the abundance spreads than prior studies.

major comments (2)
  1. [Abstract and DOHT plots section] The central temperature inference (100–150 MK or 110–120 MK) rests on the assumption that the observed abundance anticorrelations arise exclusively from proton-capture nucleosynthesis at those temperatures. No quantitative assessment of dilution by pristine gas or contributions from other channels (e.g., rotational mixing) is described, which directly affects whether the DOHT plots isolate a unique temperature window.
  2. [Results] The claim of 'stringent constraints' from the 185-star sample requires explicit demonstration that the DOHT diagnostic ratios remain insensitive to dilution factors; without model grids that include varying dilution, the narrower 110–120 MK range for AGB stars cannot be robustly distinguished from broader ranges.
minor comments (1)
  1. [Figure captions] Notation for the DOHT plots and the exact abundance ratios used should be defined more clearly in the text and figure captions to allow independent reproduction.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive comments, which help clarify the assumptions underlying the DOHT plots. We respond to each major comment below.

read point-by-point responses

  1. Referee: [Abstract and DOHT plots section] The central temperature inference (100–150 MK or 110–120 MK) rests on the assumption that the observed abundance anticorrelations arise exclusively from proton-capture nucleosynthesis at those temperatures. No quantitative assessment of dilution by pristine gas or contributions from other channels (e.g., rotational mixing) is described, which directly affects whether the DOHT plots isolate a unique temperature window.

    Authors: The DOHT diagnostics are formulated from specific abundance ratios whose extreme values require proton-capture processing at the quoted temperatures; dilution with pristine material reduces the amplitude of the anticorrelations but does not generate the high-temperature signatures themselves. We nevertheless agree that an explicit discussion of dilution and possible secondary channels would strengthen the presentation. In the revised manuscript we will add a dedicated paragraph (with illustrative dilution calculations) showing that the inferred temperature windows remain stable for dilution fractions up to ~50 % and briefly note why rotational mixing is not expected to dominate the observed patterns in this cluster. revision: yes

  2. Referee: [Results] The claim of 'stringent constraints' from the 185-star sample requires explicit demonstration that the DOHT diagnostic ratios remain insensitive to dilution factors; without model grids that include varying dilution, the narrower 110–120 MK range for AGB stars cannot be robustly distinguished from broader ranges.

    Authors: The statistical power of the 185-star sample lies in mapping the full extent of the anticorrelations, which is set by the most extreme (least diluted) stars. We accept, however, that a direct test with dilution grids is needed to substantiate the narrower AGB temperature window. The revised version will therefore include a short grid of simple dilution models applied to the AGB and massive-star yield sets, demonstrating that the 110–120 MK interval remains distinguishable even after dilution. revision: yes

Circularity Check

0 steps flagged

No significant circularity: temperature constraints derived from independent abundance data via new diagnostic plots

full rationale

The paper introduces DOHT diagnostic plots based on observed proton-capture anticorrelations in a sample of 185 stars and uses them to map abundance patterns to a temperature range for polluters. This mapping relies on external nucleosynthesis expectations rather than redefining the input data or fitting parameters that are then relabeled as predictions. No self-citation chains, self-definitional loops, or fitted-input-as-prediction reductions are present in the provided derivation. The central inference remains self-contained against the observed abundances and model comparisons.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Only abstract available; no free parameters, axioms, or invented entities can be extracted or evaluated.

pith-pipeline@v0.9.0 · 5773 in / 1073 out tokens · 22197 ms · 2026-05-25T14:47:40.162742+00:00 · methodology

discussion (0)

Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.

Reference graph

Works this paper leans on

31 extracted references · 31 canonical work pages · 1 internal anchor

  1. [1]

    1999, , 347, 572

    Arnould, M., Goriely, S., Jorissen, A. 1999, , 347, 572

    work page 1999

  2. [2]

    2015, , 810, 148

    Carretta, E. 2015, , 810, 148

    work page 2015

  3. [3]

    2018, , A614, A109 (Paper I)

    Carretta, E., Bragaglia, A. 2018, , A614, A109 (Paper I)

    work page 2018

  4. [4]

    2019a, in preparation

    Carretta, E., Bragaglia, A. 2019a, in preparation

    work page

  5. [5]

    2019b, in preparation

    Carretta, E., Bragaglia, A. 2019b, in preparation

    work page

  6. [6]

    Carretta, E., Bragaglia, A., Gratton, R.G. et al. 2007, , 464, 967

    work page 2007

  7. [7]

    2009a, , 505, 139

    Carretta, E., Bragaglia, A., Gratton, R.G., Lucatello, S. 2009a, , 505, 139

    work page

  8. [8]

    Carretta, E., Bragaglia, A., Gratton, R.G. et al. 2009b, , 505, 117

    work page

  9. [9]

    Carretta, E., Bragaglia, A., Gratton, R.G. et al. 2010, , 516, 55

    work page 2010

  10. [10]

    2012, , 760, 86

    Cohen, J.G., Kirby, E.N. 2012, , 760, 86

    work page 2012

  11. [11]

    1981, , 245, L79

    Cottrell, P.L., Da Costa, G.S. 1981, , 245, L79

    work page 1981

  12. [12]

    D'Antona, F., Vesperini, E., D'Ercole, A. et al. 2016, , 458, 2122

    work page 2016

  13. [13]

    2009, , 507, L1

    de Mink, S.E., Pols, O.R., Langer, N., Izzard, R.G. 2009, , 507, L1

    work page 2009

  14. [14]

    Decressin, T., Meynet, G., Charbonnel, C., et al.\ 2007, , 464, 1029

    work page 2007

  15. [15]

    1989, A.Tsir., 1538, 11

    Denisenkov, P.A.,& Denisenkova, S.N. 1989, A.Tsir., 1538, 11

    work page 1989

  16. [16]

    2014, MNRAS, 437, L21

    Denissenkov, P.A., Hartwick, F.D.A. 2014, MNRAS, 437, L21

    work page 2014

  17. [17]

    2003, , 404, 187

    Gratton, R.G., Carretta, E., Claudi, R., Lucatello, S., & Barbieri, M. 2003, , 404, 187

    work page 2003

  18. [18]

    2000, , 354, 169

    Gratton, R.G., Sneden, C., Carretta, E., Bragaglia, A. 2000, , 354, 169

    work page 2000

  19. [19]

    Harris, W. E. 1996, , 112, 1487

    work page 1996

  20. [20]

    2003, PASA, 20, 279

    Karakas, A.I., Lattanzio, J..C. 2003, PASA, 20, 279

    work page 2003

  21. [21]

    1993, , 105, 301

    Langer, G.E., Hoffman, R., & Sneden, C. 1993, , 105, 301

    work page 1993

  22. [22]

    M\'esz\'aros, S., Martell, S.L., Shetrone, M. et al. 2015, , 149, 153

    work page 2015

  23. [23]

    Mucciarelli, A., Bellazzini, M., Ibata, R. et al. 2012, , 426, 2889

    work page 2012

  24. [24]

    2015, , 801, 68

    Mucciarelli, A., Bellazzini, M., Merle, T., Plez, B., Dalessandro, E., Ibata, R. 2015, , 801, 68

    work page 2015

  25. [25]

    Nataf, D.M., Wyse, R., Schiavon, R.P. et al. 2019, arXiv:1904.07884

    work page internal anchor Pith review Pith/arXiv arXiv 2019

  26. [26]

    Pancino, E., Romano, D., Tang, B. et al. 2017, , 601, A112

    work page 2017

  27. [27]

    2007, , 470, 179

    Prantzos, N., Charbonnel, C., Iliadis, C. 2007, , 470, 179

    work page 2007

  28. [28]

    2017, , 608, A28

    Prantzos, N., Charbonnel, C., Iliadis, C. 2017, , 608, A28

    work page 2017

  29. [29]

    2003, , 115, 1211

    Smith, G.H., Martell, S.L. 2003, , 115, 1211

    work page 2003

  30. [30]

    D'Antona, F., Mazzitelli, I., Gratton, R

    Ventura, P. D'Antona, F., Mazzitelli, I., Gratton, R. 2001, , 550, L65

    work page 2001

  31. [31]

    2012, , 761, L30

    Ventura, P., D'Antona, F., Di Criscienzo, M., Carini, R., D'Ercole, A., Vesperini, E. 2012, , 761, L30

    work page 2012