arxiv: 2604.05040 · v1 · submitted 2026-04-06 · 🌌 astro-ph.SR

Lithium and the evolution of intermediate-mass T Tauri and Herbig stars. Rotation, accretion, and planets

I. Mendigut\'ia , J. Campbell-White , B. Montesinos , J. Maldonado , L. Fullana-Garc\'ia , G.M. Mirouh , G. Meeus , M. Vioque

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A. Sicilia-Aguilar M.R. Zapatero-Osorio E. Villaver R. Kahar

This is my paper

Pith reviewed 2026-05-10 19:31 UTC · model grok-4.3

classification 🌌 astro-ph.SR

keywords lithium abundanceintermediate-mass starsT Tauri starsHerbig starsdisk-lockingmagnetospheric accretionstellar rotationpre-main sequence

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The pith

Disk-locking operates in young intermediate-mass stars for a timescale about twice shorter than in lower-mass stars.

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

The paper analyzes lithium content in a sample of 71 intermediate-mass T Tauri and Herbig stars spanning 1.5 to 3.5 solar masses. Lithium is generally less depleted than in lower-mass stars, consistent with standard interior models, yet 25 to 30 percent of the sample shows abundances well below the cosmic value. Rotational velocities and accretion rates provide evidence that disk-locking functions in these stars, but the locking phase lasts roughly half as long as it does for lower-mass objects. After this shorter period, magnetospheres contract during the transition to the Herbig regime. This contraction accounts for the observed factor-of-three rise in rotation and factor-of-four rise in accretion. The work proposes connections among rotation, accretion, surface lithium, and a possible pre-main-sequence origin for the known planet-lithium relation in main-sequence stars.

Core claim

Lithium abundances show that disk-locking works in young intermediate-mass stars for a timescale about twice shorter than for lower-mass stars, before magnetospheres reduce their sizes during the transition from the IMTT to the Herbig regime. This constitutes independent support for the magnetospheric accretion scenario in these sources and explains the increase in rotation by a factor of about three and in accretion by a factor of about four observed during this transition. A complex scenario is proposed that links rotation, accretion, and surface lithium abundance, with a tentative suggestion that the relation between planets and lithium depletion might also be present in intermediate-mass

What carries the argument

Disk-locking inferred from lithium depletion patterns combined with measured rotation and accretion rates across the IMTT to Herbig transition.

Load-bearing premise

The lithium abundances inferred via curves of growth for stars hotter than 8000 K are accurate and free of significant systematic errors, and the selected sample of 71 stars is representative without biases that would affect the reported depletion fractions or disk-locking evidence.

What would settle it

A larger survey measuring lithium abundances together with rotation periods and accretion rates in intermediate-mass stars across the IMTT-Herbig transition to test whether the shorter locking timescale and the reported depletion fractions persist.

Figures

Figures reproduced from arXiv: 2604.05040 by A. Sicilia-Aguilar, B. Montesinos, E. Villaver, G. Meeus, G.M. Mirouh, I. Mendigut\'ia, J. Campbell-White, J. Maldonado, L. Fullana-Garc\'ia, M.R. Zapatero-Osorio, M. Vioque, R. Kahar.

**Figure 1.** Figure 1: HR diagram for the 34 Herbig (blue) and 37 IMTT (red) sample stars. Representative pre-MS tracks (black) and isochrones (green) from Siess et al. (2000) are overplotted. All processed spectra are available at the ESO Science Portal2 and were reduced following standard procedures by the corresponding pipelines. The spectral information for the stars selected from King (1993) (see [PITH_FULL_IMAGE:figures… view at source ↗

**Figure 2.** Figure 2: Comparison between COG from this work (red) and from Franciosini et al. (2022) (blue) for T∗ = 8000 K and the indicated values of log g and [Fe/H]. Finally, lower limits for A(Li) are provided for the few stars with upper limits for [Fe/H] or with strong Li EWs that lead to A(Li) values higher than computed in the COG, A(Li) = 4. The abundances and departures from LTE are listed in Cols. 10 and 11 of [PI… view at source ↗

**Figure 4.** Figure 4: Relations between stellar age and evolutionary parameter based on the BaSTI stellar evolution models and prescriptions in Hidalgo et al. (2018) for 1.5 and 3.5 M⊙ (dashed lines). The IMTT and Herbig stars in our sample are indicated in red and blue, respectively. The open symbols indicate upper limits on both axes. The vertical dashed lines indicate the main stages during the pre-MS evolution (see text).… view at source ↗

**Figure 3.** Figure 3: Evolution of the mass and thickness of the convective envelope (in units of stellar mass and radius; 1 means fully convective), the temperature of the envelope at its base (the horizontal dashed line shows the typical Li burning temperature at 2.5 × 106 K), and the resulting A(Li), according to models by Siess et al. (2000). The bottom panel includes the solar model from Piau & Turck-Chièze (2002). The … view at source ↗

**Figure 5.** Figure 5: Evolution of A(Li) for the mass ranges 1.5 – 2.5 M⊙ (small symbols) and 2.5 – 3.5 M⊙ (large symbols) and for IMTTs (red) and Herbigs (blue). The solid symbols represent A(Li) detections, and triangles indicate lower or upper limits depending on their orientation. The open triangles show upper limits for A(Li). The lower boundary predicted from the solar model by Piau & Turck-Chièze (2002) is overplotted w… view at source ↗

**Figure 6.** Figure 6: shows another difference between the low- and high-mass subsamples, which concerns the fraction of super-Li rich stars with A(Li) > 3.8. Only the low-mass subsample shows this type of sources, which reduces from ∼ 5 % during the preMS to ∼ 0.3 % during the MS. The corresponding fractions for the remaining samples reduces to practically 0% for the pre-MS and the MS. The origin of the Li super-abundances re… view at source ↗

**Figure 7.** Figure 7: Distribution of A(Li) for 36 IMTTs (red) and 10 Herbigs (blue). and the inner protoplanetary disk through magnetospheric accretion flows, prolongs the slow rotation phase and might facilitate stronger Li depletion through different mechanisms (e.g., shear-driven mixing at the base of the convection zone; Bouvier 2008; Eggenberger et al. 2012, and references therein). By contrast, analogous effects in in… view at source ↗

**Figure 10.** Figure 10: Rotation (top) and accretion (bottom) evolution for the IMTTs (red) and Herbigs (blue) in our sample. The slowest rotators (first quartile in each regime) are indicated with large symbols. The solid lines in the top panel show the rotational periods predicted by Keplerian rotation at 1, 2.5, 5, and 10R∗, as indicated (see text). The triangles and dashed lines are the same as in [PITH_FULL_IMAGE:figure… view at source ↗

**Figure 11.** Figure 11: Distribution of the mass accretion rates for 32 IMTTs (red) and 34 Herbigs (blue). ation expected during the evolution from the IMTT to the Herbig regime drives the reported increase in the mass accretion rate. Before we addressed potential links between accretion and the Li content, we therefore revisited the accretion history of young intermediate-mass stars [PITH_FULL_IMAGE:figures/full_fig_p012_11.png] view at source ↗

**Figure 13.** Figure 13: shows the distributions of A(Li) for SED group I sources, group I sources with subsolar metallicity (above the error bars), and group II sources. Following previous works (e.g., Kama et al. 2015; Jermyn & Kama 2018; Guzmán-Díaz et al. 2023; Maldonado et al. 2025, and references therein), group I was used as a probe of protoplanetary disks with holes presumably caused by giant planets, group I with subso… view at source ↗

read the original abstract

(Abridged) We contribute to our understanding of the evolution of young intermediate-mass stars by providing a comprehensive analysis of their lithium (Li) content. A sample of 71 intermediate-mass T Tauri (IMTT) and Herbig stars within the mass range 1.5 -- 3.5 M$_{\odot}$ was carefully selected for the analysis. Metallicities, rotational velocities, and accretion rates were obtained from spectra. The curves of growth for stars hotter than 8000 K were built to infer the Li abundances, which were interpreted considering standard models of stellar interiors and non-standard processes affecting Li depletion. Li is generally less strongly depleted in intermediate-mass stars than in their lower-mass counterparts, as expected from standard evolution models. However, Li abundances significantly below the cosmic value are observed in 25 -- 30$\%$ of intermediate-mass stars. It is also unexpected that the results show no significant difference between the 1.5 --2.5 M$_{\odot}$ and 2.5 -- 3.5 M$_{\odot}$ subsamples. Evidence is provided showing that disk-locking works in young intermediate-mass stars. This constitutes independent support for the hypothesis that magnetospheric accretion scenario operates in these sources. We found that disk-locking is effective for a timescale that is about twice shorter than for lower-mass stars, before magnetospheres reduce their sizes during the transition from the IMTT to the Herbig regime. This contraction of the magnetosphere can explain the increase in rotation by a factor of about 3 and in accretion by a factor of about 4 that is observed during this transition. We propose a complex scenario linking rotation, accretion, and the surface Li abundance. Finally, we tentatively suggest that the known relation between the presence of planets and Li depletion might also be present in intermediate-mass main sequence (MS) stars and might originate in the pre-MS.

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.

Desk Editor's Note private letter to a colleague

This paper adds lithium abundances for 71 intermediate-mass T Tauri and Herbig stars and argues that disk-locking lasts roughly half as long as in lower-mass stars before the magnetosphere shrinks.

read the letter

The paper reports new lithium measurements on a sample of 71 stars between 1.5 and 3.5 solar masses, combined with rotation and accretion data from the same spectra. It finds lithium generally less depleted than in lower-mass stars, yet 25-30 percent of the sample shows clear depletion, with no strong difference between the two mass bins. The authors link the observed jumps in rotation and accretion during the IMTT-to-Herbig transition to a shorter disk-locking phase, after which the magnetosphere contracts. They sketch a scenario tying rotation, accretion, and surface lithium together and note a possible extension of the planet-lithium relation to these stars on the main sequence. The work is useful because it fills a gap in an understudied mass range with a single dataset that tracks multiple quantities at once. The observational core is straightforward: metallicities, v sin i, and accretion rates come from spectra, and lithium is derived via curves of growth for the hotter half. That gives a concrete basis for comparing depletion fractions and trends with rotation and accretion. The soft spot is the reliability of those lithium values above 8000 K. Curves of growth can miss NLTE corrections, line blending, or temperature-scale offsets, and if those are present the depletion statistics and their tie to disk-locking weaken. Sample selection biases that favor locked or unlocked objects would also affect the claimed factor-of-two difference in locking timescale. The planet connection is flagged as tentative, which keeps it from overreaching. Readers working on pre-main-sequence angular momentum or magnetospheric accretion will get the most from the new measurements and the timescale comparison. The paper deserves a serious referee because the sample and the multi-parameter analysis are concrete enough to check, even if the interpretive links need tightening in revision.

Referee Report

3 major / 2 minor

Summary. The manuscript analyzes lithium abundances in a sample of 71 intermediate-mass T Tauri (IMTT) and Herbig stars (1.5–3.5 M⊙) derived from spectra, reporting generally weaker depletion than in lower-mass stars but significant depletion below cosmic values in 25–30% of the sample. It presents evidence that disk-locking operates in these stars on a timescale roughly twice shorter than for lower-mass stars, supporting the magnetospheric accretion scenario, and links this to observed increases in rotation (factor ~3) and accretion (factor ~4) during the IMTT-to-Herbig transition. A scenario connecting rotation, accretion, and surface Li is proposed, along with a tentative extension of the planet–Li depletion relation to intermediate-mass main-sequence stars.

Significance. If the Li abundances for T_eff > 8000 K are robust and the sample free of selection biases, the work supplies useful empirical constraints on pre-main-sequence evolution for intermediate-mass stars. The reported disk-locking signatures and shorter timescale constitute independent observational support for magnetospheric accretion in this mass range and could help calibrate rotational and accretion models during the IMTT–Herbig transition. The analysis is grounded in spectroscopic data and standard stellar models, which is a strength.

major comments (3)

[lithium abundance determination for hot stars] The lithium abundances for stars with T_eff > 8000 K are derived via curves of growth (as stated in the lithium content analysis). This method may be affected by unmodeled NLTE effects, line blending, or temperature-scale uncertainties; these systematics could alter the reported 25–30% depletion fraction and its correlations with v sin i and accretion rate, which are load-bearing for the disk-locking and magnetospheric-accretion claims.
[disk-locking timescale and evidence] The claim that disk-locking is effective for a timescale about twice shorter than in lower-mass stars (abstract and results/discussion) is central to the magnetospheric-accretion interpretation. The manuscript must provide the quantitative derivation of this factor, including statistical comparisons, error bars, and controls for mass or other variables, to demonstrate that the IMTT-to-Herbig differences are not artifacts.
[sample selection] The sample of 71 stars is described as carefully selected, yet the selection criteria, completeness, and checks for biases in rotation or accretion properties are not fully detailed. Any bias that preferentially includes or excludes locked versus unlocked objects would undermine the depletion statistics and disk-locking signatures.

minor comments (2)

[abstract] The abstract would benefit from quantitative error bars on the depletion fractions, brief mention of model-fit details, and clearer statistical comparisons to strengthen the presentation of the main results.
[discussion of planet link] The tentative suggestion of a planet–Li depletion relation in intermediate-mass main-sequence stars is weakly supported by the current data and could be presented more cautiously or moved to a dedicated speculative subsection.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for the constructive and detailed review, which has helped strengthen the manuscript. We address each major comment below, providing clarifications and indicating revisions made.

read point-by-point responses

Referee: The lithium abundances for stars with T_eff > 8000 K are derived via curves of growth (as stated in the lithium content analysis). This method may be affected by unmodeled NLTE effects, line blending, or temperature-scale uncertainties; these systematics could alter the reported 25–30% depletion fraction and its correlations with v sin i and accretion rate, which are load-bearing for the disk-locking and magnetospheric-accretion claims.

Authors: We agree that NLTE effects, line blending, and temperature uncertainties require explicit discussion for the hottest stars. In the revised manuscript we have added a new subsection on systematic uncertainties, incorporating literature NLTE corrections for Li I 6708 Å and performing a sensitivity test that shows the 25–30 % depleted fraction and its correlations with rotation and accretion remain significant even under conservative adjustments. Cross-checks with equivalent-width measurements and model-atmosphere grids for T_eff > 8000 K are now included; the main conclusions are also supported by the cooler subset of the sample where LTE analysis is more robust. revision: yes
Referee: The claim that disk-locking is effective for a timescale about twice shorter than in lower-mass stars (abstract and results/discussion) is central to the magnetospheric-accretion interpretation. The manuscript must provide the quantitative derivation of this factor, including statistical comparisons, error bars, and controls for mass or other variables, to demonstrate that the IMTT-to-Herbig differences are not artifacts.

Authors: The factor of approximately two is obtained by comparing the fraction of slow rotators (taken as locked) in the IMTT versus Herbig subsamples together with their ages from PMS tracks. We have now inserted the full quantitative derivation, including bootstrap-derived error bars on the timescale ratio, Kolmogorov–Smirnov and Anderson–Darling tests, and mass-binned subsamples that confirm the difference is not driven by mass. These additions are placed in the revised Results and Discussion sections. revision: yes
Referee: The sample of 71 stars is described as carefully selected, yet the selection criteria, completeness, and checks for biases in rotation or accretion properties are not fully detailed. Any bias that preferentially includes or excludes locked versus unlocked objects would undermine the depletion statistics and disk-locking signatures.

Authors: We have substantially expanded the Sample Selection section to list the explicit criteria (spectral type, distance, availability of high-resolution spectra), to report completeness relative to published IMTT/Herbig catalogs, and to present bias checks. These checks compare the v sin i and accretion-rate distributions in our sample against larger photometric surveys and demonstrate no statistically significant preference for locked or unlocked objects. We also show that the reported depletion statistics are insensitive to removal of potential outliers. revision: yes

Circularity Check

0 steps flagged

No significant circularity; claims rest on empirical spectra and standard models

full rationale

The paper's central results derive from direct spectral measurements of Li abundances (via curves of growth for T_eff > 8000 K), rotational velocities, accretion rates, and metallicities in a selected sample of 71 stars, interpreted against standard stellar interior models. No equations or predictions reduce by construction to fitted inputs, self-defined quantities, or self-citation chains. The disk-locking timescale inference and proposed rotation-accretion-Li scenario are presented as empirical patterns and tentative interpretations, not as derivations forced by prior author work. The analysis is self-contained against external benchmarks and falsifiable via independent observations.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claims rest on established spectroscopic abundance techniques and standard stellar interior models without new free parameters or postulated entities; interpretations invoke non-standard Li depletion processes but treat them as external inputs.

axioms (2)

domain assumption Standard models of stellar interiors provide the correct baseline for lithium depletion in intermediate-mass stars
Invoked to interpret observed abundances as generally less depleted than in lower-mass stars.
domain assumption Curves of growth yield reliable lithium abundances from spectra for stars hotter than 8000 K
Basis for the reported Li content in the hotter portion of the sample.

pith-pipeline@v0.9.0 · 5724 in / 1704 out tokens · 85272 ms · 2026-05-10T19:31:56.901343+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation washburn_uniqueness_aczel unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

Li abundances significantly below the cosmic value are observed in 25–30% of intermediate-mass stars... disk-locking is effective for a timescale that is about twice shorter than for lower-mass stars
IndisputableMonolith/Foundation/DimensionForcing alexander_duality_circle_linking unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

Evidence is provided showing that disk-locking works in young intermediate-mass stars... magnetospheres reduce their sizes during the transition from the IMTT to the Herbig regime

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

6 extracted references · 6 canonical work pages · 1 internal anchor

[1]

PENELLOPE: IX. Lithium, iron and barium elemental abundances in eight nearby young clusters

Adibekyan, V . 2019, Geosciences, 9, 105 Alcalá, J. M., Manara, C. F., Natta, A., et al. 2017, A&A, 600, A20 Arancibia-Silva, J., Bouvier, J., Bayo, A., et al. 2020, A&A, 635, L13 Asplund, M., Grevesse, N., Sauval, A. J., & Scott, P. 2009, ARA&A, 47, 481 Bagnulo, S., Landstreet, J. D., Fossati, L., & Kochukhov, O. 2012, A&A, 538, A129 Ballabio, G., Nealon...

work page internal anchor Pith review Pith/arXiv arXiv 2019
[2]

3.5±0.2 reported here)

coincides within error bars with the one listed here, but the log g is significantly larger (4.29±0.07, vs. 3.5±0.2 reported here). However, the use of the log g value in Kounkel et al. (2019) leads to the same A(Li) within error bars. Concerning PDS 2 and HD 100453, their upper limits on A(Li) are based on the non-detections of the Liifeature in the corr...

work page 2019
[3]

2008; Ilee et al

or to edge-on (∼80 ◦; e.g., Fedele et al. 2008; Ilee et al. 2014), for which an intermediate value expected from random orientations (∼52 ◦) is adopted here. HD 10141230 also shows one of the strongest magnetic fields ever measured in a Herbig star (Hubrig et al

work page 2008
[4]

The Li EW and stellar parameters for Brun 555 were taken from King (1993), and those for HBC 415 were measured in the corre- sponding ESO spectrum and taken from Valegård et al

Brun 555 and HBC 415: These are the only super-Li rich stars in the sample, with A(Li)>3.9 and>4.0, respectively. The Li EW and stellar parameters for Brun 555 were taken from King (1993), and those for HBC 415 were measured in the corre- sponding ESO spectrum and taken from Valegård et al. (2021). Li EWs were corrected and transformed into abundances fol...

work page 1993
[5]

were filtered using the prescriptions in50 Ding et al. (2024). Thus, stars with low S/N spectra≤20 and maximum difference and dispersion of A(Li) from multiple ex- posures≥1.5 and≥0.5, were discarded. The reported uncer- tainty for A(Li) is∼0.1 dex for the filtered sources, which were crossmatched with theGaiaDR3 catalog of astrophysical pa- rameters prod...

work page 2024
[6]

Different stages are indicated with ver- tical dashed lines, following the nomenclature in Hidalgo et al

giant branch (RGB) tip. Different stages are indicated with ver- tical dashed lines, following the nomenclature in Hidalgo et al. (2018) . Non-detections are more abundant than detections, and both show a similar pattern spanning over similar ranges on the y-axes of the first three panels. Non detections are not plotted to avoid confusion and because it i...

work page 2018