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arxiv: 2512.15672 · v3 · pith:NHIP24D7new · submitted 2025-12-17 · 🌀 gr-qc · hep-ph

Observational constraints on the spin/anisotropy of the CCOs of Cassiopeia A, Vela Jr. and G347.3-0.5 and a single surviving continuous gravitational wave candidate

Jing Ming , Maria Alessandra Papa , Heinz-Bernd Eggenstein , Bernd Machenschalk , J. Martins , B. Steltner , B. McGloughlin , V. Dergachev
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R. Prix M. Bensch
This is my paper

Pith reviewed 2026-05-16 21:27 UTC · model grok-4.3

classification 🌀 gr-qc hep-ph
keywords continuous gravitational wavesneutron starsellipticitycrustal anisotropycentral compact objectssupernova remnantsgravitational wave searchesEinstein@Home
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The pith

A deep volunteer search sets the tightest limits yet on neutron star ellipticity and crustal anisotropy in three supernova remnants, leaving one candidate signal.

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

The authors searched for continuous gravitational waves from the central compact objects in Cassiopeia A, Vela Jr. and G347.3-0.5 using LIGO O3a data processed by Einstein@Home volunteers. After initial detection of millions of candidates, they performed follow-up analyses with O3b and O4a data to validate or eliminate them through statistical tests and vetoes. This effort produced the tightest constraints so far on the gravitational wave amplitude, equatorial ellipticity for periods under 2 ms, r-mode amplitudes and crustal anisotropy in these neutron stars. The work shows that any real signal must be very weak, and identifies one remaining candidate from G347.3-0.5 whose status needs checking with newer observations.

Core claim

We set the most stringent constraints to date on the gravitational-wave amplitude, equatorial ellipticity, r-mode saturation amplitude, and neutron-star crustal anisotropy for the first time. For spin periods lower than 2 ms we constrain the ellipticity to be smaller than 4×10^{-7} for all targets. We exclude crustal anisotropy values larger than 5×10^{-3} for spin periods between 1.3-100 ms. Only one candidate from the G347.3 search survives all follow-ups.

What carries the argument

The hierarchical multi-stage follow-up procedure applied to candidates from the initial wide-parameter search, using independent data segments for confirmation.

If this is right

  • Ellipticity upper limits reach below 4×10^{-7} for all three sources at spin periods under 2 ms.
  • Crustal anisotropy is ruled out above 5×10^{-3} for periods from 1.3 to 100 ms.
  • The search yields improved bounds on gravitational wave strain and r-mode saturation amplitudes.
  • One candidate signal persists after all vetting stages and awaits further data analysis.

Where Pith is reading between the lines

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

  • Confirmation or rejection of the surviving candidate could be achieved by applying the same search to O4b data when it becomes available.
  • These anisotropy constraints may help discriminate between different models of neutron star crust rigidity.
  • Extending the approach to additional young neutron stars could map the distribution of ellipticities across the population.
  • If the candidate proves real, it would represent the first detected continuous gravitational wave from a central compact object.

Load-bearing premise

Any genuine continuous gravitational wave signal from these neutron stars would survive the multi-stage follow-up process in O3b and O4a data without being rejected by the applied vetoes or thresholds.

What would settle it

Reanalysis of the phase parameters of the surviving candidate using the O4b and O4c datasets to determine whether the signal remains consistent or is excluded.

Figures

Figures reproduced from arXiv: 2512.15672 by Bernd Machenschalk, B. McGloughlin, B. Steltner, Heinz-Bernd Eggenstein, Jing Ming, J. Martins, Maria Alessandra Papa, M. Bensch, R. Prix, V. Dergachev.

Figure 1
Figure 1. Figure 1: Number of templates searched in 1-Hz bands as a function of signal frequency. In the legend we also show the total number of templates searched for each target in the low and high frequency bands. up searches are preformed on the in-house Atlas super￾computing cluster (B. Allen 2025). 6.1. Stage-0 and candidate selection After a work-unit is complete, the host returns to the Einstein@Home project the top-r… view at source ↗
Figure 2
Figure 2. Figure 2 [PITH_FULL_IMAGE:figures/full_fig_p008_2.png] view at source ↗
Figure 4
Figure 4. Figure 4: Distributions of R a from all the G347.3 searches. and [PITH_FULL_IMAGE:figures/full_fig_p009_4.png] view at source ↗
Figure 3
Figure 3. Figure 3: Distributions of R a from all the Vela Jr. searches. a shorter Tcoh = 360 hours, compared to the 720 hours of the Stage-0 Vela Jr. search. The shorter coherent baseline of the Cas A search results in a larger differ￾ence in coherence time between the Stage-0 and Stage-1 searches, which produces a clearer separation between the R1 of the test-signals and the noise-dominated ones of the search results, shown… view at source ↗
Figure 5
Figure 5. Figure 5: Upper limits on the gravitational wave amplitude of continuous gravitational wave signals from our search for Cas A (red triangles) as a function of frequency, compared to other recent results. The horizontal lines show the indirect age-based upper limits corresponding to braking indexes of 5 and 7. & K. Riles 2024; C. Salvadore et al. 2025; J. Ming et al. 2024; J. Morales et al. 2025). Cas A : our results… view at source ↗
Figure 7
Figure 7. Figure 7: Upper limits on the gravitational wave amplitude of continuous gravitational wave signals from our search for G347.3 (red triangles) as a function of frequency, compared to other recent results. The horizontal lines show the indirect age-based upper limits corresponding to braking indexes of 5 and 7. Above 1300 Hz, our results beat the previous most sen￾sitive results (C. Salvadore et al. 2025) by about 4.… view at source ↗
Figure 8
Figure 8. Figure 8: 90 % upper limits on the ellipticity (a) and r– mode amplitude (b) of the three targets as the function of gravitational wave signal frequency f (twice of the spin fre￾quency ν). For Vela Jr. we show two curves, corresponding to two distance estimates: 200 pc and 750 pc. For Cas A, we assume 3.4 kpc. where c is the speed of light, G the gravitational con￾stant, I the moment of inertia about the spin axis o… view at source ↗
Figure 9
Figure 9. Figure 9: Constraints on the neutron-star spin frequency/crustal anisotropy. All frequencies to the right of the vertical dashed lines—up to 1500 Hz—are excluded by our search. The dashed curves denote the frequency-dependent braking index n, whose values are shown on the right-hand side Y axis. All the other curves and points’ values are read from the left-hand side Y axis. slower birth spins. Using pulsars associa… view at source ↗
Figure 10
Figure 10. Figure 10: Excluded regions in the (ν0, ν) plane inferred from our most constraining ellipticity upper limits for Vela Jr. assuming d = 200 pc. Shaded areas indicate combinations of birth spin frequency ν0 and current spin frequency ν that are ruled out; blue and magenta correspond to ⟨ϕ⟩ = 5 × 10−3 and ⟨ϕ⟩ = 5 × 10−5 , respectively (overlap indicates exclusion for both values of ⟨ϕ⟩). Vertical white gaps denote fre… view at source ↗
Figure 11
Figure 11. Figure 11: O3a+b Bayesian follow-up posteriors and credible intervals around the maximum likelihood estimator. Allen, B. 2025,, https://www.aei.mpg.de/25950/computer-clusters Allen, G. E., Chow, K., DeLaney, T., et al. 2014, The Astrophysical Journal, 798, 82, doi: 10.1088/0004-637x/798/2/82 Anderson, D. 2004, in Fifth IEEE/ACM International Workshop on Grid Computing, 4–10, doi: 10.1109/GRID.2004.14 Anderson, D. P.… view at source ↗
read the original abstract

We carry out the deepest and broadest search for continuous gravitational-wave signals from three neutron stars at the center of the supernova remnants Cassiopeia A, Vela Jr., and G347.3-0.5. This search was made possible by the computing power shared by thousands of Einstein@Home volunteers. After the initial Einstein@Home search, which used O3a data, we perform a multi-stage follow-up of the most promising $\approx$ 45 million signal candidates. In the last stages, we use independent data (O3b and O4a) to further investigate the remaining candidates from the previous stages. We set the most stringent constraints to date on the gravitational-wave amplitude, equatorial ellipticity, r-mode saturation amplitude, and -- for the first time -- the neutron-star crustal anisotropy. For spin periods lower than 2 ms we constrain the ellipticity to be smaller than $4\times 10^{-7}$ for all targets. We exclude crustal anisotropy values larger than $5\times 10^{-3}$ for spin periods between 1.3--100 ms. Only one candidate -- from the G347.3 search -- survives all follow-ups. We illustrate properties of this candidate. Investigations on new data will aid in clarifying its nature. Such ``new" data already exist, O4b and O4c, and would be optimal for this purpose, but they are not publicly accessible at the time of writing. In the appendix we provide our estimate of the candidate phase parameters, which are useful for others to carry out checks on the new data.

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

0 major / 1 minor

Summary. The manuscript reports results from the deepest Einstein@Home search for continuous gravitational waves from the central compact objects in Cassiopeia A, Vela Jr., and G347.3-0.5. An initial O3a search is followed by multi-stage follow-up of ~45 million candidates using independent O3b and O4a data; the analysis sets the most stringent upper limits to date on gravitational-wave strain amplitude, equatorial ellipticity, r-mode saturation amplitude, and (for the first time) neutron-star crustal anisotropy, while identifying a single surviving candidate from the G347.3-0.5 search whose phase parameters are supplied for external verification.

Significance. If the reported upper limits hold, the work delivers the tightest observational bounds yet on several key neutron-star parameters, including the first direct constraints on crustal anisotropy for spin periods 1.3–100 ms. The multi-stage pipeline with independent data segments follows established continuous-wave methods, the use of volunteer computing enables the required depth, and explicit provision of candidate phase parameters supports falsifiability on future public data releases.

minor comments (1)
  1. §4 and the appendix: the description of the final veto thresholds and the exact definition of the anisotropy parameter could be cross-referenced more explicitly to aid readers reproducing the ellipticity-to-anisotropy conversion.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript, including the recognition of the depth of the Einstein@Home search, the multi-stage follow-up procedure, and the provision of candidate parameters for external verification. We are pleased that the referee recommends acceptance.

Circularity Check

0 steps flagged

No significant circularity in data-driven upper limits

full rationale

The paper reports results from a multi-stage Einstein@Home search on independent LIGO O3a/O3b/O4a strain data segments. Upper limits on gravitational-wave amplitude, ellipticity, r-mode amplitude, and crustal anisotropy are computed directly from the loudest surviving candidates after vetoes and statistical thresholds, without any parameter fitting that re-uses the target quantities as inputs. The single surviving candidate is supplied with explicit phase parameters for external verification on new data. No equations reduce by construction to prior results, no self-citations are load-bearing for the central constraints, and the pipeline follows standard, externally documented methods. The derivation chain is therefore self-contained against the input data.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central results rest on standard general-relativity waveform models and LIGO noise statistics; no new free parameters are introduced or fitted to the target data.

axioms (2)
  • standard math General relativity accurately describes continuous gravitational-wave emission from rotating neutron stars
    Invoked throughout the waveform templates and signal model in the search pipeline.
  • domain assumption LIGO detector noise is stationary and Gaussian over the analyzed segments after cleaning
    Required for the matched-filter statistics and false-alarm probability estimates.

pith-pipeline@v0.9.0 · 5655 in / 1264 out tokens · 27782 ms · 2026-05-16T21:27:48.481614+00:00 · methodology

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  1. [1]

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  3. [3]

    GWTC-4.0: Updating the Gravitational-Wave Transient Catalog with Observations from the First Part of the Fourth LIGO-Virgo-KAGRA Observing Run

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    work page internal anchor Pith review Pith/arXiv arXiv doi:10.1103/physrevd.70.082001 2017