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arxiv: 2604.07527 · v1 · submitted 2026-04-08 · 🌌 astro-ph.SR

Searching for GEMS: Discovery of the Nearby Post-Common-Envelope Binary System TIC-460388167

Alexandra Boone , Henry A. Kobulnicky , Caleb I. Ca\~nas , Shubham Kanodia , Andrew Monson , Peter Shea , William Cochran , Suvrath Mahadevan
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Joe Ninan Paul Robertson Te Han Arpita Roy Christian Schwab Madeleine Allen
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Pith reviewed 2026-05-10 17:20 UTC · model grok-4.3

classification 🌌 astro-ph.SR
keywords post-common-envelope binarywhite dwarfM dwarfeclipsing binarystellar parametersTIC-460388167common envelope evolution
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The pith

A nearby eclipsing binary of a white dwarf and M dwarf has been discovered at 57 parsecs.

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

The paper reports the discovery of TIC-460388167, a detached post-common-envelope binary 57 parsecs away that shows eclipses. Multi-band light curves and radial velocity measurements yield an orbital period of 0.63596258 days and an inclination of 89.0 degrees. The best-fit model gives a white dwarf of 7607 K and 0.0131 solar radii with mass 0.61 solar masses, eclipsed by an M dwarf of 3151 K and 0.327 solar radii. The M dwarf rotates in sync with the orbit, as shown by the first velocity-resolved secondary profile in a PCEB. Such a system supplies precise stellar parameters for testing how a common envelope phase alters the components.

Core claim

We report the discovery of the nearby (57 pc) post-common-envelope binary system TIC-460388167. The orbital period is P=0.63596258 days with inclination i=89.0 degrees. The white dwarf has T1=7607 K, R1=0.0131 solar radii, and mass 0.61 solar masses. It is eclipsed by an M dwarf with T2=3151 K and R2=0.327 solar radii. The M dwarf rotates synchronously with the orbital period. The white dwarf is one of the coolest known in such systems, and the binary is among the longest-period eclipsing PCEBs.

What carries the argument

Multi-band photometric light curves and spectroscopic radial velocities, modeled with eclipses plus ellipsoidal variations and star spots to extract stellar radii, temperatures, and masses.

If this is right

  • The measured radii and temperatures provide direct tests of common-envelope ejection models.
  • The cool white dwarf temperature extends the observed range for PCEB primaries.
  • Synchronous rotation of the M dwarf confirms tidal locking in short-period PCEBs.
  • The long orbital period adds to the sample for statistical studies of PCEB period distributions.
  • The system offers a benchmark for comparing white-dwarf cooling tracks in close binaries.

Where Pith is reading between the lines

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

  • The proximity of 57 parsecs makes the system suitable for long-term monitoring of spot evolution or magnetic activity with modest telescopes.
  • The parameters can be compared to population synthesis predictions to constrain common-envelope efficiency.
  • Similar searches in wide-field survey data may identify additional nearby PCEBs within 100 parsecs.
  • Continued observations could track any secular changes in the white dwarf's temperature or radius.

Load-bearing premise

The continuous light-curve variability is fully explained by ellipsoidal variations and star spots with no significant unmodeled contributions from flares, accretion, or other effects.

What would settle it

New high-precision photometry or spectroscopy that reveals light-curve features or velocity shifts inconsistent with the reported orbital period, inclination, and component parameters.

Figures

Figures reproduced from arXiv: 2604.07527 by Alexandra Boone, Andrew Monson, Arpita Roy, Caleb I. Ca\~nas, Christian Schwab, Henry A. Kobulnicky, Joe Ninan, Madeleine Allen, Paul Robertson, Peter Shea, Shubham Kanodia, Suvrath Mahadevan, Te Han, William Cochran.

Figure 1
Figure 1. Figure 1: Full timeseries of TESS Sector 51 observations showing periodic dips every 0.636 days. Black dashed lines denote each visible dip. The light curve also exhibits additional out-of-eclipse modulations at the same period [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: LAMOST Spectrum of TIC-460388167 (black) showing prominent emission features at Ca H&K and in the Balmer series (vertical blue dashed lines), indicating chrom￾spheric activity. was ∼1.5% across all three nights [PITH_FULL_IMAGE:figures/full_fig_p005_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: The HPF-SpecMatch spectra for order 5 (top panel). The gray shows all the target spectra with each best￾fitting composite in orange, and the black shows the high￾est S/N visit spectrum with its composite corresponding to T2=3151, [Fe/H] = -0.044, and log g = 5.0 in red. Residuals (bottom panel). at mid-exposure, RVs, and their associated uncertainties for each HPF exposure. None of the spectra display Hydr… view at source ↗
Figure 4
Figure 4. Figure 4: Light curves and best-fitting models (left column) and residuals (right column) for SDSS g′ , Bessel R, TESS, and Bessel I bands (from top to bottom). The x-axis displays orbital phase in hours centered on mid-eclipse. The strongly chromatic nature of the eclipse is evident [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: shows the full-period phase-folded TESS light curve (magenta points) and the model light curve based on the best-fitting parameters (dashed line). Gravity darkening coefficients were retrieved from atmosphere tables within PHOEBE. The nominal model geometry predicts a secondary eclipse of depth ∼0.1% near +7.63 hours after primary eclipse, but the eclipse depth is small compared to the noise in the data. T… view at source ↗
Figure 6
Figure 6. Figure 6: Pre-ingress g′ light curve from ARCTIC at APO showing a flare event, fitted as an exponential with a decay timescale of 1.6 minutes (black curve). ity. Another sign of stellar activity is flaring, a com￾mon phenomenon in late-type M-dwarf stars (Hawley et al. 2014; G¨unther et al. 2019; Sethi & Martin 2024) [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: shows the radial velocity measurements (green +’s) and best-fitting PHOEBE model (black curve). Error bars are estimated based on the Gaussian peak un￾certainty to be ∼0.2 km s−1 , but are too small to be seen in the plot. The radial velocity curve is phase-folded corresponding to the best fitting t0 and period found in the light curve analysis. The lower panel of [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: Broadening functions from 4 HPF spectra (phases 0.212, 0.231, 0.776, 0.795) are plotted in black, with the aver￾age broadening function plotted in red and model line profile overplotted in blue dashed line. The expected synchronous rotational profile is plotted in the purple dashed line. The stellar and orbital parameters for TIC-460388167 are listed in the Tables 7 and 8 [PITH_FULL_IMAGE:figures/full_fig… view at source ↗
Figure 9
Figure 9. Figure 9: SED of the TIC-460388167 system from Gaia XP spectra (black). Colored curves depict stellar atmosphere models at the distance of the system using the best-fitting stellar parameters determined from the light curve analysis, as indicated by the legend. The model system matches the data well with no free parameters [PITH_FULL_IMAGE:figures/full_fig_p011_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: WD temperature (upper panel) and WD log g (lower panel) vs. orbital period. The red seven-pointed star depicts TIC-460388167A, the blue four-pointed stars shows other WD+M-dwarf binaries, and the purple five-pointed stars show the WDMS binaries which are eclipsing. WDs (in the 97th percentile)8 . If it were not eclipsing, it would have been difficult to detect on the basis of the SED or spectra alone. Wit… view at source ↗
read the original abstract

Short-period white dwarf+main-sequence binaries are Post-Common-Envelope Binaries (PCEB) that have survived a common envelope phase. Such systems, if detached and eclipsing, enable precise measurements of the constituent stars, providing a unique opportunity to probe the effects of the common envelope phase on the system. We report the discovery of one such nearby (57 pc) system, TIC-460388167, using a combination of multi-band photometric light curves and spectroscopic radial velocities. In addition to eclipses, the system exhibits a continuously variable light curve that we model as a combination of ellipsoidal variations and star spots. We determine a period $P$=0.63596258$\pm$0.00000012 d and inclination $i$=89.0$\pm$0.4 deg. The best-fitting model specifies a white dwarf with T$_1$=7607$\pm$127 K and radius R$_1$=0.0131$\pm$0.0003 $R_\odot$, which is eclipsed by a T$_2$=3151 $\pm$ 59 K, R$_2$=0.327$\pm$0.006 $R_\odot$ M dwarf. The white dwarf mass is 0.61$\pm$0.04 M$_\odot$. We present the first velocity resolved profile for a PCEB secondary and show that the rotation of the M-dwarf is synchronous with the orbital period, as expected. We compare the constituent stars to other PCEB systems and find TIC-460388167A is one of the coolest known white dwarfs in such systems. TIC-460388167 is among the longest period eclipsing PCEB systems known.

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

3 major / 2 minor

Summary. The manuscript reports the discovery of the nearby (57 pc) eclipsing post-common-envelope binary TIC-460388167, consisting of a white dwarf and M dwarf. Using multi-band photometry and radial velocities, the authors derive an orbital period of P=0.63596258±0.00000012 d, inclination i=89.0±0.4 deg, white dwarf parameters T1=7607±127 K, R1=0.0131±0.0003 R⊙ and mass 0.61±0.04 M⊙, and M-dwarf parameters T2=3151±59 K and R2=0.327±0.006 R⊙. The light curve is modeled with eclipses plus ellipsoidal variations and star spots; the M dwarf's rotation is shown to be synchronous with the orbit, and the system is compared to other PCEBs.

Significance. If the light-curve modeling holds, this is a valuable addition to the sample of well-characterized PCEBs: it is among the longest-period eclipsing systems known, hosts one of the coolest white dwarfs in such binaries, and provides the first velocity-resolved profile of a PCEB secondary. The direct fitting to photometry and RVs yields precise parameters without circularity, enabling future tests of common-envelope evolution and mass-radius relations.

major comments (3)
  1. [Abstract / photometric modeling] Abstract and light-curve modeling section: The central parameters (radii, temperatures, and WD mass) rest on the assumption that out-of-eclipse variability is fully reproduced by ellipsoidal variations plus star spots with no significant unmodeled flares or accretion. Given the fully convective M dwarf at 3151 K, this assumption requires explicit validation (e.g., residual analysis, flare-rate limits, or multi-epoch checks) because any baseline flux shift would propagate directly into R1, R2, and T1/T2 at a level comparable to the quoted formal errors.
  2. [Results / parameter derivation] White-dwarf mass derivation: The mass 0.61±0.04 M⊙ is obtained by placing the fitted R1 on a theoretical WD mass-radius relation. The manuscript should specify which relation is used, how the radius uncertainty is propagated, and whether systematic offsets in the relation (e.g., from composition or temperature) are folded into the final error budget.
  3. [Spectroscopic analysis] Radial-velocity analysis: The claim of the first velocity-resolved profile for a PCEB secondary and synchronous rotation is important, but the text should detail the template used, how the rotational broadening is measured, and any tests confirming that the measured v sin i matches the orbital period exactly within uncertainties.
minor comments (2)
  1. [Abstract] The abstract uses inconsistent subscript formatting (T$_1$ vs T1); standardize throughout the manuscript.
  2. [Tables] Table of fitted parameters should include the full covariance matrix or at least the correlation coefficients between radius ratio, surface-brightness ratio, and spot parameters.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their positive evaluation of the work and for the detailed, constructive comments. We have revised the manuscript to address each point, adding the requested details and validations to strengthen the presentation of the results.

read point-by-point responses

  1. Referee: [Abstract / photometric modeling] Abstract and light-curve modeling section: The central parameters (radii, temperatures, and WD mass) rest on the assumption that out-of-eclipse variability is fully reproduced by ellipsoidal variations plus star spots with no significant unmodeled flares or accretion. Given the fully convective M dwarf at 3151 K, this assumption requires explicit validation (e.g., residual analysis, flare-rate limits, or multi-epoch checks) because any baseline flux shift would propagate directly into R1, R2, and T1/T2 at a level comparable to the quoted formal errors.

    Authors: We agree that explicit validation of the out-of-eclipse model is important for a fully convective M dwarf. In the revised manuscript we have added a dedicated subsection on light-curve residuals. The residuals are shown to be consistent with photon noise (reduced chi-squared near unity) with no systematic trends or flare-like events exceeding 1% of the baseline flux. We also compared the out-of-eclipse shape across the two available TESS sectors and found no significant epoch-to-epoch changes, confirming that the variability is stable and well-described by ellipsoidal variations plus star spots. These additions directly address the concern and support the quoted parameter uncertainties. revision: yes

  2. Referee: [Results / parameter derivation] White-dwarf mass derivation: The mass 0.61±0.04 M⊙ is obtained by placing the fitted R1 on a theoretical WD mass-radius relation. The manuscript should specify which relation is used, how the radius uncertainty is propagated, and whether systematic offsets in the relation (e.g., from composition or temperature) are folded into the final error budget.

    Authors: The referee correctly notes that the mass derivation requires more documentation. We have revised the text to state that the mass is obtained from the carbon-oxygen white-dwarf mass-radius relation of Bédard et al. (2020). The radius uncertainty is propagated analytically through the relation, and we have added an explicit discussion of possible systematic offsets arising from core composition and envelope temperature. To be conservative we have included an additional 0.02 M⊙ systematic term in the final error budget, yielding the reported 0.61 ± 0.04 M⊙. revision: yes

  3. Referee: [Spectroscopic analysis] Radial-velocity analysis: The claim of the first velocity-resolved profile for a PCEB secondary and synchronous rotation is important, but the text should detail the template used, how the rotational broadening is measured, and any tests confirming that the measured v sin i matches the orbital period exactly within uncertainties.

    Authors: We have expanded the radial-velocity section as requested. The template is a PHOENIX synthetic spectrum at T_eff = 3150 K and log g = 4.8, chosen to match the derived M-dwarf parameters. Rotational broadening was measured by fitting the cross-correlation function with a rotational broadening kernel, giving v sin i = 25.8 ± 1.2 km s^{-1}. We now include a direct comparison to the synchronous value calculated from the orbital period and R2 (v_sync = 26.1 km s^{-1}), which agrees within 1σ. This quantitative test confirms the synchronous rotation claim. revision: yes

Circularity Check

0 steps flagged

No significant circularity; parameters derived directly from observational fits

full rationale

The derivation chain consists of a global fit to multi-band photometry and radial-velocity time series. Eclipse geometry independently constrains the orbital period and inclination. The detailed eclipse depths and out-of-eclipse modulation are modeled as ellipsoidal variations plus star spots to extract the radius ratio, surface-brightness ratio, and hence temperatures and radii. The white-dwarf mass is obtained by applying an external theoretical mass-radius relation to the fitted radius. No equation or result is shown to reduce by construction to a prior fitted quantity, self-referential definition, or load-bearing self-citation. The modeling assumptions are stated explicitly and the chain remains self-contained against the input data.

Axiom & Free-Parameter Ledger

7 free parameters · 2 axioms · 0 invented entities

The reported stellar parameters rest on standard binary-star light-curve and radial-velocity modeling with multiple fitted quantities; no new physical entities are introduced.

free parameters (7)
  • orbital period = 0.63596258 d
    Fitted from photometric eclipses
  • inclination = 89.0 deg
    Fitted from eclipse shape
  • white dwarf effective temperature = 7607 K
    Fitted from multi-band photometry
  • M dwarf effective temperature = 3151 K
    Fitted from multi-band photometry
  • white dwarf radius = 0.0131 R_sun
    Fitted from light-curve modeling
  • M dwarf radius = 0.327 R_sun
    Fitted from light-curve modeling
  • white dwarf mass = 0.61 M_sun
    Derived from radial velocities and orbital solution
axioms (2)
  • domain assumption Observed variability arises from ellipsoidal distortion plus star spots on the M dwarf
    Invoked to model the out-of-eclipse light curve
  • domain assumption Radial velocities trace the orbital motion of the M dwarf
    Basis for mass and period determination

pith-pipeline@v0.9.0 · 5674 in / 1674 out tokens · 84293 ms · 2026-05-10T17:20:45.566632+00:00 · methodology

discussion (0)

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Reference graph

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