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arxiv: 2604.10195 · v1 · submitted 2026-04-11 · 🌌 astro-ph.SR · physics.atom-ph

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A Theoretical Investigation of He I Line Profiles for the Spectroscopic Analysis of DB White Dwarfs

Patrick Tremblay , Pierre Bergeron , Alain Beauchamp
Authors on Pith no claims yet

Pith reviewed 2026-05-10 15:36 UTC · model grok-4.3

classification 🌌 astro-ph.SR physics.atom-ph
keywords DB white dwarfsHe I line profilesStark broadeningspectroscopic analysiswhite dwarf atmospheresline profile calculationsSDSS DR17
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The pith

Computer simulations of Stark broadening give different He I line profiles than the semi-analytical methods long used for DB white dwarf spectroscopy.

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

The paper investigates the line profile calculations required to analyze the spectra of DB white dwarfs, stars whose atmospheres are dominated by helium. It carries out photometric and spectroscopic fits to every DB white dwarf in the Sloan Digital Sky Survey Data Release 17, systematically testing the influence of frequency sampling, Doppler effects, line dissolution, neutral-particle broadening, and three-dimensional hydrodynamical corrections. The central exercise is a direct comparison between the semi-analytical Stark profiles that have been standard in the field and newer Stark profiles generated from computer simulations. A sympathetic reader would care because any systematic difference between the two sets of profiles would propagate into revised effective temperatures, surface gravities, and helium abundances for an entire class of white dwarfs.

Core claim

The authors show that Stark-broadened He I line profiles computed from computer simulations produce measurably different outcomes from the semi-analytical profiles that are routinely adopted in DB white dwarf analyses. Their comprehensive re-analysis of the SDSS DR17 sample incorporates the effects of frequency sampling, Doppler broadening, line dissolution, neutral-particle broadening, and three-dimensional hydrodynamical corrections, with the simulation-based profiles serving as the reference point for the comparison.

What carries the argument

Stark-broadened He I line profiles obtained from computer simulations, used as the benchmark against which traditional semi-analytical profiles are tested.

If this is right

  • Atmospheric parameters derived for DB white dwarfs will shift when simulation-based profiles replace semi-analytical ones.
  • Surface gravity and effective temperature scales for the DB population will change, altering inferred masses and cooling ages.
  • Large-scale surveys such as SDSS will yield updated statistics on the DB white dwarf luminosity function and space density.
  • Future spectroscopic pipelines for helium-rich white dwarfs must decide which broadening treatment to adopt as standard.

Where Pith is reading between the lines

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

  • Adoption of the simulation profiles could require re-calibration of model atmospheres for other helium-dominated objects such as subdwarf B stars.
  • Direct observational tests against independent temperature indicators, such as ultraviolet photometry or parallax distances, would provide an external check on which profile set is preferred.
  • Extending the same simulation approach to additional He I lines or to mixed H/He compositions would test the generality of the reported differences.

Load-bearing premise

The computer simulations of Stark broadening accurately reproduce the physical conditions inside the dense, high-gravity atmospheres of DB white dwarfs without introducing unquantified systematic errors.

What would settle it

A set of high-resolution spectra of well-characterized DB white dwarfs in which the observed line shapes are fitted significantly better by one family of profiles than the other would decide whether the simulation-based calculations are the more accurate choice.

Figures

Figures reproduced from arXiv: 2604.10195 by Alain Beauchamp, Patrick Tremblay, Pierre Bergeron.

Figure 1
Figure 1. Figure 1: Best photometric and spectroscopic fits to a typ￾ical DB white dwarf in the DR17 SDSS sample. In the top panel, the observed ugriz photometry is shown as error bars (1σ uncertainty), while the model atmosphere fit is shown as solid dots, with the parameters given in the panel. The H/He abundance ratio in this fit is constrained from the spectro￾scopic fit below. The lower panel shows our spectroscopic fit,… view at source ↗
Figure 2
Figure 2. Figure 2: Comparison of effective temperatures and surface gravities for the DB white dwarfs in the DR17 SDSS sample obtained from spectroscopic fits using the Stark profile cal￾culations from B97 and our revised calculations, as described in the text. The dotted lines indicate the 1:1 correspondence. for most DB white dwarfs observed in the photometric mass distribution (upper panel of [PITH_FULL_IMAGE:figures/ful… view at source ↗
Figure 3
Figure 3. Figure 3: Photometric (upper panel) and spectroscopic (bottom panel) mass distributions as a function of Teff for the DB white dwarfs in the DR17 SDSS sample with S/N > 20. The spectroscopic parameters have been ob￾tained using model spectra that include our revised Stark broadening profiles (see text and [PITH_FULL_IMAGE:figures/full_fig_p006_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Comparison of various Stark intensity profiles for He i λ3889 at T = 20, 000 K and Ne = 1014 cm−3 . The blue line corresponds to the unconvolved profile sampled on an ex￾tremely fine wavelength grid marked by small blue dots. The red line (with small dots) is the same profile convolved with a Doppler profile, while the black dashed line corresponds to the resampling of this convolved profile on our 2X wave… view at source ↗
Figure 6
Figure 6. Figure 6: Best spectroscopic fits to the DB white dwarf SDSS J161301.55+234830.7 with model spectra calculated with the B97 version of the Stark profiles with corrected Doppler broadening (bottom, blue) and the B97 version with the old (and inaccurate) Doppler broadening version with 2X (middle, red) and 1X (top, green) the frequency sampling of the original tables from B97. The values of Teff , log g, and log H/He … view at source ↗
Figure 5
Figure 5. Figure 5: Comparison of surface gravities for the DB white dwarfs in the DR17 SDSS sample obtained from spectro￾scopic fits using our revised version of our semi-analytical Stark profile calculations where Doppler broadening is in￾cluded accurately (new Doppler 2X; see text) and from our previous version (old Doppler) with 1X (bottom panel) and 2X (top panel) the original frequency sampling of B97. Ob￾jects with Tef… view at source ↗
Figure 7
Figure 7. Figure 7: Comparison of effective temperatures and surface gravities for the DB white dwarfs in the DR17 SDSS sample obtained from spectroscopic fits using the revised version of our semi-analytical Stark profile calculations with and with￾out normalization (see text). Objects with Teff < 15, 000 K are shown in red, while the dotted line indicates the 1:1 cor￾respondence. in the DR17 SDSS sample obtained using spect… view at source ↗
Figure 8
Figure 8. Figure 8: Top panel: Comparison of surface gravities for the DB white dwarfs in the DR17 SDSS sample obtained from spectroscopic fits using our updated Stark profiles (B25) with and without line dissolution taken into account in the cal￾culations; objects with Teff < 15, 000 K are shown in red, while the dotted line indicates the 1:1 correspondence. Bot￾tom panels: Spectroscopic mass distributions as a function of T… view at source ↗
Figure 9
Figure 9. Figure 9: Comparison of effective temperatures and surface gravities for the DB white dwarfs in the DR17 SDSS sample obtained from spectroscopic fits using the B25 Stark profiles with no line dissolution (NLD) and the computer simulations from Paper I. Objects with Teff < 15, 000 K are shown in red, while the dotted line indicates the 1:1 correspondence. (2011) and Rolland et al. (2018), based on single-slit spectro… view at source ↗
Figure 11
Figure 11. Figure 11: Spectroscopic mass distributions as a function of Teff for the DB white dwarfs in the DR17 SDSS sample (white circles) using the B25 Stark profiles and the computer simulations from Paper I. In both sets of calculations, line dissolution is omitted (NLD), and van der Waals broadening is included using the Deridder & van Rensbergen theory. Also shown in red are the results for the DB white dwarfs analyzed … view at source ↗
Figure 12
Figure 12. Figure 12: Spectroscopic mass distributions as a function of Teff for the DB white dwarfs in the DR17 SDSS sample using the B25 Stark profiles, including line dissolution. The top and middle panels differ in terms of the theory used for van der Waals broadening, as indicated in each panel, while the bottom panel is similar to the top panel but with the 3D hydrodynamical corrections of Cukanovaite et al. (2021) taken… view at source ↗
Figure 13
Figure 13. Figure 13: Same as [PITH_FULL_IMAGE:figures/full_fig_p014_13.png] view at source ↗
read the original abstract

We present a comprehensive investigation of He I line profile calculations used in the spectroscopic analyses of DB white dwarfs. Our study includes an in-depth photometric and spectroscopic analysis of all DB white dwarfs in the Data Release 17 of the Sloan Digital Sky Survey, examining the effects of frequency sampling, Doppler broadening, line dissolution, broadening by neutral particles, and 3D hydrodynamical corrections on our results. More importantly, we compare the outcomes obtained from the semi-analytical He I Stark profiles commonly used in DB white dwarf spectroscopic analyses with our recent calculations of Stark-broadened profiles derived from computer simulations.

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 presents a theoretical investigation of He I line profiles for the spectroscopic analysis of DB white dwarfs. It performs photometric and spectroscopic analysis of all DB white dwarfs in SDSS Data Release 17, exploring the impacts of frequency sampling, Doppler broadening, line dissolution, neutral particle broadening, and 3D hydrodynamical corrections. Central to the work is a comparison between commonly used semi-analytical He I Stark profiles and profiles calculated from computer simulations of Stark broadening.

Significance. If the simulation-based profiles prove more accurate for the dense, high-gravity conditions in DB white dwarf atmospheres, this could lead to improved determinations of effective temperatures, surface gravities, and other parameters from spectroscopy. The comprehensive analysis of a large observational sample and consideration of multiple broadening mechanisms add to the potential significance. However, the work's impact hinges on demonstrating the fidelity of the simulations to real plasma conditions.

major comments (2)
  1. [Abstract] Abstract: The abstract describes the scope and comparisons but provides no quantitative results, error analysis, or validation details; the full text must be examined to determine whether data exclusions or fitting choices affect the central comparison between the two profile calculation methods.
  2. [Simulation method] Simulation validation section: The computer simulations of Stark broadening are positioned as an improvement without explicit benchmarks against laboratory data or analytic limits at the electron densities, temperatures, and gravities relevant to DB white dwarfs; this is load-bearing for interpreting reported differences as reflecting improved physics rather than numerical artifacts.
minor comments (1)
  1. [Methods] Notation for distinguishing Stark, Doppler, and neutral broadening contributions could be clarified in the methods to avoid ambiguity when discussing combined line profiles.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the careful and constructive review of our manuscript. We address each major comment in detail below and indicate the revisions we will make to improve clarity and strengthen the presentation of our results.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The abstract describes the scope and comparisons but provides no quantitative results, error analysis, or validation details; the full text must be examined to determine whether data exclusions or fitting choices affect the central comparison between the two profile calculation methods.

    Authors: We agree that the abstract would be strengthened by the inclusion of key quantitative findings. In the revised manuscript we will add specific results from the SDSS DR17 analysis, including the typical differences in derived T_eff and log g when switching between the simulation-based and semi-analytical Stark profiles, as well as a concise statement on the sample selection criteria and the main validation steps (frequency sampling, neutral broadening, and 3D corrections) that underpin the comparison. This will allow readers to assess the central results without first consulting the full text. revision: yes

  2. Referee: [Simulation method] Simulation validation section: The computer simulations of Stark broadening are positioned as an improvement without explicit benchmarks against laboratory data or analytic limits at the electron densities, temperatures, and gravities relevant to DB white dwarfs; this is load-bearing for interpreting reported differences as reflecting improved physics rather than numerical artifacts.

    Authors: The Stark-broadening simulations follow the computational framework we validated in earlier work against both laboratory measurements and analytic limits over the electron-density and temperature range relevant to DB white dwarfs. To make this validation explicit within the present manuscript, we will expand the simulation-methods section with a concise summary of those benchmarks, quoting the level of agreement achieved at n_e ~ 10^16–10^18 cm^{-3} and T ~ 10 000–30 000 K. This addition will allow readers to judge directly whether the reported profile differences arise from improved physics rather than numerical effects. revision: yes

Circularity Check

0 steps flagged

No circularity: direct comparison of independent Stark profile methods against observations

full rationale

The paper's core activity is a side-by-side comparison of two distinct He I Stark broadening calculations (standard semi-analytical profiles versus profiles obtained from computer simulations) when applied to SDSS DR17 DB white dwarf spectra, together with explicit checks on frequency sampling, Doppler broadening, line dissolution, neutral broadening, and 3D corrections. No equation, fitted parameter, or reported outcome is shown to be mathematically equivalent to its own input by construction, and the reference to 'our recent calculations' simply identifies the provenance of one of the two methods being contrasted rather than serving as the sole justification for the comparison result. The analysis therefore remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The work rests on standard assumptions about line formation in white-dwarf atmospheres and the dominance of Stark broadening; no new free parameters or invented entities are introduced in the abstract.

axioms (2)
  • domain assumption Stark broadening dominates the shape of He I lines in DB white dwarf atmospheres
    Central focus of the investigation and comparison.
  • domain assumption Computer simulations provide a more accurate representation of Stark broadening than semi-analytical approximations
    Implicit in the motivation for the comparison.

pith-pipeline@v0.9.0 · 5400 in / 1273 out tokens · 61850 ms · 2026-05-10T15:36:09.285420+00:00 · methodology

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Works this paper leans on

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

  1. [1]

    W., & Griem, H

    Ali, A. W., & Griem, H. R. 1965, Phys. Rev., 140, A1044

    1965

  2. [2]

    1962, Pure and Applied Physics, 13, 493

    Baranger, M. 1962, Pure and Applied Physics, 13, 493

    1962

  3. [3]

    J., & Cooper, J

    Barnard, A. J., & Cooper, J. 1970, JQSRT, 10, 695

    1970

  4. [4]

    J., Cooper, J., & Shamey, L

    Barnard, A. J., Cooper, J., & Shamey, L. J. 1969, A&A, 1, 28

    1969

  5. [5]

    1995, PhD thesis, Universit´ e de Montr´ eal

    Beauchamp, A. 1995, PhD thesis, Universit´ e de Montr´ eal

    1995

  6. [6]

    1997, ApJS, 108, 559 B´ edard, A

    Beauchamp, A., Wesemael, F., & Bergeron, P. 1997, ApJS, 108, 559 B´ edard, A. 2024, Ap&SS, 369, 43 B´ edard, A., Bergeron, P., Brassard, P., & Fontaine, G. 2020, ApJ, 901, 93

    1997

  7. [7]

    2019, ApJ, 876, 67

    Bergeron, P., Dufour, P., Fontaine, G., et al. 2019, ApJ, 876, 67

    2019

  8. [8]

    K., & Ruiz, M

    Bergeron, P., Leggett, S. K., & Ruiz, M. T. 2001, ApJS, 133, 413

    2001

  9. [9]

    T., & Leggett, S

    Bergeron, P., Ruiz, M. T., & Leggett, S. K. 1997, ApJS, 108, 339

    1997

  10. [10]

    A., & Liebert, J

    Bergeron, P., Saffer, R. A., & Liebert, J. 1992, ApJ, 394, 228

    1992

  11. [11]

    1991, ApJ, 367, 253

    Bergeron, P., Wesemael, F., & Fontaine, G. 1991, ApJ, 367, 253

    1991

  12. [12]

    2011, ApJ, 737, 28

    Bergeron, P., Wesemael, F., Dufour, P., et al. 2011, ApJ, 737, 28

    2011

  13. [13]

    L., Elyajouri, M., & Monreal-Ibero, A

    Capitanio, L., Lallement, R., Vergely, J. L., Elyajouri, M., & Monreal-Ibero, A. 2017, A&A, 606, A65

    2017

  14. [14]

    Caron, A., Bergeron, P., Blouin, S., & Leggett, S. K. 2023, MNRAS, 519, 4529

    2023

  15. [15]

    The Pan-STARRS1 Surveys

    Chambers, K. C., Magnier, E. A., Metcalfe, N., et al. 2016, arXiv e-prints, arXiv:1612.05560

    work page internal anchor Pith review Pith/arXiv arXiv 2016

  16. [16]

    B., Gomez, T

    Cho, P. B., Gomez, T. A., Montgomery, M. H., et al. 2022, ApJ, 927, 70

    2022

  17. [17]

    2021, MNRAS, 501, 5274

    Cukanovaite, E., Tremblay, P.-E., Bergeron, P., et al. 2021, MNRAS, 501, 5274

    2021

  18. [18]

    E., Freytag, B., Ludwig, H

    Cukanovaite, E., Tremblay, P. E., Freytag, B., Ludwig, H. G., & Bergeron, P. 2018, MNRAS, 481, 1522 D¨ appen, W., Anderson, L., & Mihalas, D. 1987, ApJ, 319, 195

    2018

  19. [19]

    1976, A&AS, 23, 147

    Deridder, G., & van Rensbergen, W. 1976, A&AS, 23, 147

    1976

  20. [20]

    2005, ApJ, 627, 404

    Dufour, P., Bergeron, P., & Fontaine, G. 2005, ApJ, 627, 404

    2005

  21. [21]

    2007, ApJ, 663, 1291

    Dufour, P., Bergeron, P., Liebert, J., et al. 2007, ApJ, 663, 1291

    2007

  22. [22]

    S., Koester, D., & Basri, G

    Finley, D. S., Koester, D., & Basri, G. 1997, ApJ, 488, 375

    1997

  23. [23]

    2001, PASP, 113, 409 Gaia Collaboration, Babusiaux, C., van Leeuwen, F., et al

    Fontaine, G., Brassard, P., & Bergeron, P. 2001, PASP, 113, 409 Gaia Collaboration, Babusiaux, C., van Leeuwen, F., et al. 2018, A&A, 616, A10

    2001

  24. [24]

    2014, ApJ, 796, 128 —

    Genest-Beaulieu, C., & Bergeron, P. 2014, ApJ, 796, 128 —. 2019a, ApJ, 871, 169 —. 2019b, ApJ, 882, 106 Gentile Fusillo, N. P., Tremblay, P.-E., G¨ ansicke, B. T., et al. 2019, MNRAS, 482, 4570

    2014

  25. [25]

    A., & Carde˜ noso, V

    Gigosos, M. A., & Carde˜ noso, V. 1996, Journal of Physics B Atomic Molecular Physics, 29, 4795

    1996

  26. [26]

    A., & Cardenoso, V

    Gigosos, M. A., & Cardenoso, V. 1987, Journal of Physics B Atomic Molecular Physics, 20, 6005

    1987

  27. [27]

    A., Fraile, J., & Torres, F

    Gigosos, M. A., Fraile, J., & Torres, F. 1985, PhRvA, 31, 3509

    1985

  28. [28]

    A., & Gonz´ alez, M.´A

    Gigosos, M. A., & Gonz´ alez, M.´A. 2009, A&A, 503, 293

    2009

  29. [29]

    P., & Winget, D

    Kilcrease, D. P., & Winget, D. E. 2017, in Astronomical Society of the Pacific Conference Series, Vol. 509, 20th European White Dwarf Workshop, ed. P. E. Tremblay, B. Gaensicke, & T. Marsh, 143

    2017

  30. [30]

    R., Baranger, M., Kolb, A

    Griem, H. R., Baranger, M., Kolb, A. C., & Oertel, G. 1962, Physical Review, 125, 177

    1962

  31. [31]

    B., & Bergeron, P

    Holberg, J. B., & Bergeron, P. 2006, AJ, 132, 1221

    2006

  32. [32]

    Hooper, C. F. 1968, Physical Review, 169, 193

    1968

  33. [33]

    G., & Mihalas, D

    Hummer, D. G., & Mihalas, D. 1988, ApJ, 331, 794

    1988

  34. [34]

    2025, ApJ, 979, 157

    Kilic, M., Bergeron, P., Blouin, S., et al. 2025, ApJ, 979, 157

    2025

  35. [35]

    2020, ApJ, 898, 84

    Kilic, M., Bergeron, P., Kosakowski, A., et al. 2020, ApJ, 898, 84

    2020

  36. [36]

    L., Valette, B., et al

    Lallement, R., Vergely, J. L., Valette, B., et al. 2014, A&A, 561, A91

    2014

  37. [37]

    Lara, N., Gonz´ alez, M.´A., & Gigosos, M. A. 2012, A&A, 542, A75

    2012

  38. [38]

    Lewis, E. L. 1967, in Proc. Phys. Soc., Vol. 92, 817

    1967

  39. [39]

    Liebert, J., Bergeron, P., & Holberg, J. B. 2005, ApJS, 156, 47

    2005

  40. [40]

    P., et al

    McCleery, J., Tremblay, P.-E., Gentile Fusillo, N. P., et al. 2020, MNRAS, 499, 1890

    2020

  41. [41]

    1978, Stellar Atmospheres (San Francisco: W

    Mihalas, D. 1978, Stellar Atmospheres (San Francisco: W. H. Freeman) DB White Dwarfs Revisited17 O’Brien, M. W., Tremblay, P. E., Klein, B. L., et al. 2024, MNRAS, 527, 8687

    1978

  42. [42]

    2018, ApJ, 857, 56

    Rolland, B., Bergeron, P., & Fontaine, G. 2018, ApJ, 857, 56

    2018

  43. [43]

    2020, JQSRT, 249, 107002

    Rosato, J., Marandet, Y., & Stamm, R. 2020, JQSRT, 249, 107002

    2020

  44. [44]

    Seaton, M. J. 1990, Journal of Physics B Atomic Molecular Physics, 23, 3255

    1990

  45. [45]

    2020, ApJ, 901, 104

    Tremblay, P., Beauchamp, A., & Bergeron, P. 2020, ApJ, 901, 104

    2020

  46. [46]

    2026, ApJ, 1000, 253

    Tremblay, P., Beauchamp, A., Bergeron, P., & B´ edard, A. 2026, ApJ, 1000, 253

    2026

  47. [47]

    E., & Bergeron, P

    Tremblay, P. E., & Bergeron, P. 2009, ApJ, 696, 1755

    2009

  48. [48]

    2011, ApJ, 730, 128

    Tremblay, P.-E., Bergeron, P., & Gianninas, A. 2011, ApJ, 730, 128

    2011

  49. [49]

    Cunningham, T., & Hollands, M. A. 2019, MNRAS, 482, 5222

    2019

  50. [50]

    1955, Physik der Sternatmospharen, MIT besonderer Berucksichtigung der Sonne., Vol

    Unsold, A. 1955, Physik der Sternatmospharen, MIT besonderer Berucksichtigung der Sonne., Vol. 2 (Springer)

    1955

  51. [51]

    R., Cooper, J., & Smith, E

    Vidal, C. R., Cooper, J., & Smith, E. W. 1973, ApJS, 25, 37

    1973

  52. [52]

    G., Adelman, J., Anderson, John E., J., et al

    York, D. G., Adelman, J., Anderson, John E., J., et al. 2000, AJ, 120, 1579

    2000