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arxiv: 2604.24113 · v1 · submitted 2026-04-27 · 🌌 astro-ph.SR

Physical Parameters of 146 Contact Binaries Derived from Light and Radial Velocity Curves

Kai Li , Xiang Gao , Si-Rui Wang , Li-Heng Wang This is my paper

Pith reviewed 2026-05-08 01:53 UTC · model grok-4.3

classification 🌌 astro-ph.SR
keywords contact binariesmass ratio distributionangular momentum lossbinary evolutionWilson-Devinney modelingLAMOST spectraTESS photometryfill-out factor
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The pith

Orbital angular momentum distribution in 146 contact binaries supports their formation from detached systems via angular momentum loss.

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

The paper derives physical parameters for 146 contact binaries by jointly modeling their light curves and medium-resolution radial velocity curves. It shows that the more massive stars are typically unevolved main-sequence objects while the less massive ones are oversized and overluminous. The resulting orbital angular momentum distribution aligns with expectations for systems that began as detached binaries and spiraled inward through angular momentum loss until they made contact. The work also flags 38 low mass ratio systems, including 11 extreme cases below q=0.15, and one standout object with q=0.113 and 98.3 percent fill-out that may be on the verge of merging.

Core claim

Through simultaneous Wilson-Devinney modeling of photometric data from ASAS-SN and TESS together with radial velocities from LAMOST spectra, the physical parameters of 146 contact binaries were obtained. The more massive components are generally less-evolved main-sequence stars while the less massive components are oversized and overluminous. The orbital angular momentum distribution matches the expected trend for formation from detached binaries via angular momentum loss. Thirty-eight systems have mass ratios below 0.25 and eleven below 0.15, with ASASSN-V J111451.48+005038.6 showing q=0.113 and the highest reported fill-out factor of 98.3 percent; eleven high mass ratio systems were also找到

What carries the argument

Simultaneous Wilson-Devinney modeling of light curves and radial velocity curves to extract masses, radii, fill-out factors, and orbital angular momentum for each system.

If this is right

  • The more massive stars remain on the main sequence while the less massive stars appear inflated and overluminous.
  • Thirty-eight systems with q below 0.25, including eleven with q below 0.15, represent a population of potential future mergers.
  • ASASSN-V J111451.48+005038.6 with q=0.113 and 98.3 percent fill-out is a strong near-merger candidate.
  • Eleven high mass ratio systems with low fill-out factors indicate recent arrival at the contact phase.
  • Several empirical relations between masses, radii, periods, and fill-out factors are derived from the sample.

Where Pith is reading between the lines

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

  • The sample provides a benchmark for testing binary population synthesis codes that model angular momentum loss rates and contact binary lifetimes.
  • Extreme low mass ratio objects can serve as test cases for common-envelope ejection and merger simulations.
  • Repeating the analysis on larger samples from future time-domain surveys would map how the mass ratio distribution evolves with age.
  • Follow-up high-cadence photometry on the record fill-out system could detect the onset of merger-driven variability.

Load-bearing premise

The assumption that the Wilson-Devinney simultaneous fit to light and radial velocity data recovers the true masses, radii, and fill-out factors without large systematic errors from model choices such as common-envelope geometry or synchronous rotation.

What would settle it

Independent high-resolution spectroscopic masses or precise eclipse-timing masses for ASASSN-V J111451.48+005038.6 that differ substantially from the reported q=0.113 would falsify the identification of such extreme low-mass-ratio contact systems.

Figures

Figures reproduced from arXiv: 2604.24113 by Kai Li, Li-Heng Wang, Si-Rui Wang, Xiang Gao.

Figure 1
Figure 1. Figure 1: The CCF curves and their fitting of three targets. The panels from left to right correspond to single, double, and triple Gaussian fits, respectively. medium resolution. The low-resolution mode, initiated in October 2011, provides a spectral resolution of R ∼ 1800 and covers a wavelength range from 3700 ˚A to 9000 ˚A. In this mode, the targets span an r-band magnitude range of 9.0 to 17.5 mag. The medium-r… view at source ↗
Figure 2
Figure 2. Figure 2: The RV and LC fittings of two targets (ASASSN-V J045519.63+451421.6 and ASASSN-V J151019.89+534339.9) are shown as examples view at source ↗
Figure 3
Figure 3. Figure 3: The M-L and M-R distributions of the 146 targets are shown in the upper ones. ZAMS and TAMS described by solid and dashed lines are also displayed in this figure. The total mass versus Jorb is plotted in the lower one. The dashed line is boundary line between detached and contact binaries derived by Eker et al. (2006) and detached binaries are also from Eker et al. (2006). a binary, semi-major axis, the te… view at source ↗
Figure 4
Figure 4. Figure 4: The relations of q − R2/R1, q − L2/L1, q − f, log P − log LT , P − a, and P − T1 for the 146 contact binaries. The red circle in the q − R2/R1 figure is deleted during the fitting view at source ↗
read the original abstract

We present a comprehensive analysis of 146 contact binaries using medium-resolution LAMOST spectra and photometric data from the All-Sky Automated Survey for SuperNovae (ASAS-SN) and the Transiting Exoplanet Survey Satellite (TESS). Radial velocity curves obtained through the cross-correlation function method were modeled simultaneously with the light curves using the Wilson-Devinney code to derive the physical parameters of these systems. The reliability of our results was verified through comparison with previous studies of ten systems, showing good agreement. Our analysis shows that the more massive components are generally less-evolved main-sequence stars, whereas the less massive components tend to be over-sized and over-luminous, consistent with earlier findings. The distribution of orbital angular momentum supports the scenario in which contact binaries form from detached binaries via angular momentum loss. We identified 38 low mass ratio ($q < 0.25$) systems, 11 of which have extremely low mass ratios ($q < 0.15$). A remarkable example is ASASSN-V J111451.48+005038.6, which exhibits a mass ratio of 0.113 and the highest fill-out factor (98.3%) reported to date, making it a strong candidate for future mergers. Conversely, we also identified 11 high mass ratio (H-type) systems, including ASASSN-V J093921.74+390452.6 - the system with the highest spectroscopically confirmed mass ratio ($q = 0.993$) and a low fill-out factor (1.8%), suggesting it recently entered the contact phase. Additionally, several empirical relations between physical parameters are established.

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 analyzes 146 contact binaries by deriving radial velocities from medium-resolution LAMOST spectra via the cross-correlation function method and performing simultaneous Wilson-Devinney modeling with ASAS-SN and TESS light curves to obtain physical parameters (masses, radii, fill-out factors, etc.). Results are verified against 10 previously studied systems showing good agreement; the orbital angular momentum distribution is used to support formation of contact binaries from detached systems via angular momentum loss; 38 low-q (q<0.25) systems are identified (11 with q<0.15), including an extreme case with q=0.113 and 98.3% fill-out factor, along with 11 high-q systems and several empirical parameter relations.

Significance. If the derived parameters prove robust, the large sample with spectroscopic constraints would substantially strengthen the observational support for the AML evolutionary scenario through the reported J_orb distribution, while providing a valuable catalog of low-q systems (including the noted extreme example) for merger studies. Explicit credit is given for the direct verification against 10 prior systems and the scale of the homogeneous analysis.

major comments (2)
  1. [§3 (Radial velocity derivation and Wilson-Devinney modeling)] §3 (Radial velocity derivation and Wilson-Devinney modeling): The central claim that the J_orb distribution supports AML-driven evolution from detached binaries requires reliable q and a values, especially for the 38 q<0.25 systems. The manuscript does not adequately demonstrate that medium-resolution CCF RVs are free from systematic biases (line blending, template mismatch, or non-synchronous effects) at low q; any offset would directly alter the computed orbital angular momenta and the reported trend relative to detached binaries.
  2. [§4 (Results on parameter distributions)] §4 (Results on parameter distributions): While agreement is shown for 10 comparison systems, the paper provides insufficient detail on data quality cuts applied to select the 146 systems, formal error propagation from the simultaneous fits, and sensitivity tests to modeling assumptions (e.g., common-envelope geometry, fixed synchronous rotation, neglect of spots). These are load-bearing for the robustness of the low-q statistics and J_orb claim.
minor comments (1)
  1. [Abstract] The abstract refers to 'several empirical relations' without naming them; the main text should explicitly list the relations (e.g., between mass ratio and fill-out factor), report their correlation coefficients or fits, and indicate statistical significance.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed and constructive review of our manuscript. The comments have helped us identify areas where additional clarification and analysis will strengthen the presentation of our methods and results. We address each major comment below and indicate the revisions we will make.

read point-by-point responses

  1. Referee: §3 (Radial velocity derivation and Wilson-Devinney modeling): The central claim that the J_orb distribution supports AML-driven evolution from detached binaries requires reliable q and a values, especially for the 38 q<0.25 systems. The manuscript does not adequately demonstrate that medium-resolution CCF RVs are free from systematic biases (line blending, template mismatch, or non-synchronous effects) at low q; any offset would directly alter the computed orbital angular momenta and the reported trend relative to detached binaries.

    Authors: We appreciate the referee's emphasis on the reliability of the derived mass ratios and semi-major axes for the low-q systems, as these underpin the J_orb analysis. The CCF method applied to the medium-resolution LAMOST spectra follows standard practice for contact binary studies, and we have verified our full set of physical parameters against ten previously published systems, finding good agreement across a range of mass ratios. This external validation provides indirect support for the absence of large systematic offsets. Nevertheless, we acknowledge that an explicit discussion of potential biases (e.g., line blending at low q or template mismatch) is warranted. In the revised manuscript we will add a dedicated paragraph in §3 that (i) quantifies the typical RV precision achieved, (ii) describes the template selection procedure, and (iii) notes that any residual non-synchronous effects would primarily affect the less-massive component, whose contribution to J_orb is already small. We will also qualify the J_orb trend statement to reflect these uncertainties while noting that the overall distribution still aligns with the AML scenario. revision: partial

  2. Referee: §4 (Results on parameter distributions): While agreement is shown for 10 comparison systems, the paper provides insufficient detail on data quality cuts applied to select the 146 systems, formal error propagation from the simultaneous fits, and sensitivity tests to modeling assumptions (e.g., common-envelope geometry, fixed synchronous rotation, neglect of spots). These are load-bearing for the robustness of the low-q statistics and J_orb claim.

    Authors: We agree that greater transparency on sample selection and error analysis is needed. In the revised manuscript we will expand §2 and §4 to include: (1) the precise photometric and spectroscopic quality cuts (S/N thresholds, phase coverage, and rejection criteria) that reduced the initial LAMOST sample to the final 146 systems; (2) a summary table of the formal 1σ uncertainties returned by the Wilson-Devinney code for the key parameters (q, a, fill-out factor, etc.); and (3) the results of additional sensitivity runs in which we varied the assumed synchronous rotation, introduced plausible spot configurations, and tested alternative common-envelope geometries. These tests will be presented for a representative subset of the low-q systems. We believe these additions will directly address the referee's concern regarding the robustness of the reported statistics. revision: yes

Circularity Check

0 steps flagged

No circularity: parameters derived from new data via standard external code

full rationale

The paper obtains component masses, radii, and orbital angular momenta by simultaneous Wilson-Devinney fitting of fresh LAMOST CCF radial velocities and ASAS-SN/TESS photometry for 146 systems. These fitted values are then used to compute J_orb and inspect its distribution; the distribution itself is an empirical summary of the fitted quantities, not an input that is redefined or predicted by the paper's own equations. Verification against ten previously published systems is external comparison, not self-referential. No self-citation chain, ansatz smuggling, or fitted-input-renamed-as-prediction is present in the derivation chain.

Axiom & Free-Parameter Ledger

2 free parameters · 1 axioms · 0 invented entities

Based solely on abstract; central claims rest on standard assumptions of the Wilson-Devinney code for contact binaries and per-system fitting of parameters such as mass ratio and fill-out factor. No invented entities or author-specific axioms are evident.

free parameters (2)
  • mass ratio q
    Fitted parameter in Wilson-Devinney modeling for each of the 146 systems.
  • fill-out factor
    Derived/fitted from combined light and velocity curve modeling.
axioms (1)
  • domain assumption Wilson-Devinney code assumptions for contact binaries including common envelope, synchronous rotation, and standard limb darkening laws
    Invoked implicitly by use of the code for simultaneous light and RV curve fitting.

pith-pipeline@v0.9.0 · 5609 in / 1654 out tokens · 48093 ms · 2026-05-08T01:53:54.822072+00:00 · methodology

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Reference graph

Works this paper leans on

3 extracted references · 3 canonical work pages

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