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REVIEW 3 major objections 5 minor 15 references

This paper argues that all known quasi-periodic eruptions have periods too long and secondaries too light to ring LISA's gravitational-wave band, so coincident detections will require a rare class of short-period 'golden' QPEs.

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2026-08-01 23:35 UTC pith:E4X5PG5F

load-bearing objection Useful QPE-LISA review with a new Poisson tension estimate, but the 5σ framing and the luminosity-based exclusion of compact secondaries need tightening. the 3 major comments →

arxiv 2607.15360 v1 pith:E4X5PG5F submitted 2026-07-16 astro-ph.HE gr-qc

Multimessenger prospects of quasi-periodic eruptions

Vojt\v{e}ch Witzany , Alessia Franchini , Matteo Bonetti , Luca Broggi This is my paper
classification astro-ph.HE gr-qc
keywords quasi-periodic eruptionsextreme mass ratio inspiralsLISAgravitational wavesmultimessenger astronomytidal disruption eventsX-ray transientssupermassive black holes
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

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

The paper examines the leading model that quasi-periodic eruptions (QPEs) are the X-ray signatures of extreme mass-ratio inspirals (EMRIs) into supermassive black holes, and asks whether those same sources could be detected by the space-based gravitational-wave observatory LISA. It argues that the answer is no for the currently known population: every known QPE has a recurrence period that puts the corresponding gravitational-wave frequency outside LISA's most sensitive range, and the X-ray luminosities point to main-sequence stars as the impacting bodies, while LISA is biased toward heavier compact objects. If this is right, the current QPE sample will not provide the long-sought electromagnetic counterparts to LISA EMRIs, and only short-period 'golden' QPEs could bridge the gap. The paper also quantifies a significant tension for the alternative scenario where the secondary is an intermediate-mass black hole, and outlines what a coordinated search strategy would need to accomplish before LISA launches.

Core claim

All known QPEs exhibit recurrence periods that are too long for the corresponding gravitational-wave signal to fall within LISA's optimal sensitivity band, and the population of secondaries favored by QPE luminosities (sun-like main-sequence stars) is exactly the population that is either tidally disrupted before reaching millihertz frequencies or too light to be detected by LISA's selection bias. The paper concludes that currently known QPEs are generally not expected to have gravitational-wave counterparts detectable by LISA, and that the only viable bridge is a rare class of short-period 'golden' QPEs with recurrence times of tens of minutes.

What carries the argument

The central argument rests on three coupled relations: (1) an order-of-magnitude black-body luminosity estimate that sets the QPE emission radius at roughly one solar radius, which rules out neutron stars and white dwarfs as secondaries unless the orbit is grazing; (2) the tidal-disruption criterion, which shows that main-sequence stars are destroyed before their orbital frequency reaches about one millihertz, the lower edge of LISA's band; and (3) the signal-to-noise scaling for inspirals, proportional to sqrt(M_sec*M_bh)/D_L, which strongly biases LISA toward heavier compact-object secondaries. Together these create a population mismatch between the sources that make QPEs and the sources L

Load-bearing premise

The load-bearing premise is that QPE luminosity requires an emission region about the size of the Sun, and therefore a large secondary radius, which rules out compact objects; if eruptions can be produced by neutron stars or black holes through a different mechanism, the claimed population mismatch between QPEs and LISA EMRIs loses much of its force.

What would settle it

Find a luminous QPE (soft X-ray luminosity around 10^42 erg/s) with a recurrence period below about 30 minutes, and show that its secondary is a neutron star or stellar-mass black hole rather than a main-sequence star. Such a source would place its gravitational-wave fundamental frequency inside LISA's band and directly contradict the paper's claim that known QPEs and LISA EMRIs are disjoint. Alternatively, a confirmed gravitational-wave detection from LISA coincident with any currently known QPE would refute the central conclusion.

Watch this falsifier — get emailed when new claim-graph text bears on it.

If this is right

  • If the central claim holds, electromagnetic counterparts to LISA EMRIs from QPEs will be rare; the QPE and LISA EMRI populations are largely disjoint.
  • A null detection of gravitational waves from a well-characterized QPE would still provide useful astrophysical information, constraining the secondary mass and potentially ruling out the EMRI model for that source.
  • Discovery of short-period 'golden' QPEs would enable bright-siren cosmology, precise black-hole mass and spin measurements, and tests of accretion-disk physics through phase dephasing.
  • The intermediate-mass-black-hole secondary interpretation of short-period QPEs is in significant tension with the observed number of such sources, at roughly 2 to 5 sigma depending on survey completeness assumptions.
  • Future lower-frequency gravitational-wave observatories, such as a LISA-like concept with much longer arms, could detect the longer-period population of QPE sources that LISA cannot hear.

Where Pith is reading between the lines

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

  • If QPE emission does not actually require a large secondary radius (for instance, if some eruption mechanism operates for compact objects without a grazing orbit), the population disparity weakens and the prospects for coincident detections improve.
  • The paper's conclusion implies that current QPE catalogs, used as tracers of EMRI activity, are heavily biased toward long-period systems; population models must account for this selection effect before drawing conclusions about EMRI rates.
  • A targeted search for periods of about 1000 seconds in existing X-ray archives, using the epoch-folding method the paper demonstrates, could provide a cheap test of the 'golden' QPE hypothesis before LISA launches.
  • The same logic extends to other repeating nuclear transients, such as millihertz quasi-periodic oscillations, which could serve as additional electromagnetic counterparts to LISA EMRIs even if known QPEs do not.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. This review/handbook chapter examines whether quasi-periodic eruptions (QPEs) in galactic nuclei can be detected as electromagnetic counterparts of extreme mass ratio inspirals (EMRIs) by LISA. The authors argue that known QPEs have recurrence periods too long for their fundamental GW frequency to lie in LISA's optimal sensitivity band, and that the luminosities of QPE eruptions favor main-sequence stellar secondaries, whereas LISA is biased toward heavier compact objects. They introduce a Poisson likelihood estimate for the intermediate-mass black hole (IMBH) scenario, finding a 2–5σ tension depending on the assumed disk-bearing fraction and survey completeness. The paper also discusses eccentricity harmonics that could make some individual sources (e.g., RX J1301) detectable, and outlines future search strategies for short-period 'golden' QPEs.

Significance. If the assessment holds, this paper provides an important cautionary note for the multimessenger community: coincident QPE–EMRI detections with LISA are likely rare, and current QPE catalogs are not promising targets. The Poisson estimate in Sec. 3.2.3 is a novel, transparent, and order-of-magnitude calculation that quantifies the tension with the IMBH hypothesis. The paper is thorough, openly lists uncertainties, and cites a broad range of relevant literature. Its main value is as a critical review that synthesizes timing, luminosity, and population arguments; even if individual estimates are model-dependent, the qualitative conclusion is likely robust within the leading star–disk collision framework.

major comments (3)
  1. [3.1.3, Eq. (9); 3.2; 6] The luminosity-based exclusion of compact secondaries is load-bearing for the population-disparity pillar of the central claim. The relation R_char ≈ max(R_sec, R_BHL) is an assumption from specific EMRI models; if the characteristic emission radius is instead set by, e.g., the disk scale height or a cooling radius, a white dwarf or neutron star could reproduce the observed QPE luminosities, and the claimed population disparity would weaken. The paper itself acknowledges 'somewhat related' but the Conclusion states the disparity as a main finding. The authors should either provide a more quantitative robustness discussion (e.g., how the conclusion changes if the emission radius is not tied to the secondary size) or explicitly qualify the Conclusion as conditional on the star–disk collision model.
  2. [3.2.3, Eqs. (15)–(16)] The significance calculation uses Wilks' theorem to convert a Poisson likelihood ratio into a Gaussian significance Z. With N_obs=3 and expected counts Λ~0.6 or smaller, the conditions for Wilks' theorem (large sample, interior null) are not clearly met. The 5σ claim for f_disk=1e-3, f_short_compl≲0.15 should be presented as a conditional consistency check, not as a rigorous statistical rejection. The authors could easily replace Wilks with an exact Poisson p-value, which would be more appropriate and would not change the qualitative conclusion.
  3. [3.2.2] The text states that a main-sequence star will be tidally disrupted 'near or below the lower edge of the LISA frequency band at ~1 mHz.' This is inconsistent with Sec. 2.2, where the LISA band is described as starting at ~0.1 mHz. The tidal disruption frequency for a solar-type star is of order 0.1 mHz, not 1 mHz. The qualitative argument (stars are disrupted before reaching the LISA sweet spot) survives, but the numerical statement should be corrected to avoid a factual error.
minor comments (5)
  1. [3.1.1, Eq. (5)] Eq. (5) appears to be a typographical rendering of the Peters (1964) period-decay formula; as written it contains an extra factor of M (the total mass) instead of sqrt(M). The subsequent Eq. (6) has the correct scaling, so this is a presentation issue, but it should be fixed.
  2. [5.1] The text reports a false-alarm probability of <6.5e-7 based on 1e5 Monte Carlo runs. With only 1e5 trials, the minimum measurable false-alarm probability is ~1e-5 (or ~3e-5 at 95% confidence for zero detections). The claim of <6.5e-7 is unsupported unless a different method was used; please clarify.
  3. [6 (and abstract)] The abstract and conclusion state 'all known QPEs exhibit recurrence periods that are too long for the corresponding GW signal to fall within the optimal sensitivity band of LISA.' Section 3.3, however, gives the example of RX J1301 with a >35 Msun BH and e≈0.25, where higher-order harmonics could enter the LISA band. The wording is saved by 'optimal' and 'generally,' but consider adding an explicit caveat to avoid overstatement.
  4. [3.2.3] The treatment of eRO-QPE2, RX J1301, and GSN 069 as a single homogeneous IMBH population is an assumption; their detailed timing and spectral properties differ (e.g., long-short patterns, duty cycle). A brief justification of why a multimodal population is not considered would strengthen the Poisson estimate.
  5. [General] There are a few leftover encoding artifacts in the text (e.g., 'uni00000037' sequences) that should be cleaned in the final version. Reference list and citations appear complete, but please double-check the spelling of author names such as 'Lui' vs 'Liu' and 'Zajaček'.

Circularity Check

0 steps flagged

No significant circularity: the central no-overlap conclusion is anchored to external LISA sensitivity curves, Peters waveform formulas, and QPE catalogs; self-citations appear only as parallel support.

full rationale

Walking the derivation chain, no load-bearing step reduces to its own inputs. The period-based pillar compares observed QPE recurrence times to the LISA sensitivity band from Robson et al. 2019 (Sec. 2.2, Fig. 2) and uses Peters 1964 waveforms (Eqs. 5-6, 13); none of those quantities are fitted to the conclusion. The population-disparity pillar (Sec. 3.1.3) does invert observed luminosities and temperatures in Eq. (9) to infer R_char ~ Rsun, and then assumes R_char is set by the secondary's physical or Bondi-Hoyle radius. That is an order-of-magnitude model assumption, and the paper itself flags it ('The exact initial size of these bubbles might differ depending on the assumed model'), but it is not a circular derivation: the luminosity data are external, the black-body formula is independent, and the size-radius link is attributed equally to Linial & Metzger (2023) and to the authors' own Franchini et al. (2023). The IMBH tension (Eqs. 13-16) is an independent consistency estimate with explicitly stated completeness and disk-fraction parameters, not a fitted prediction. The Section 5.1 epoch-folding demonstration is a synthetic illustration of detectability and does not enter the central claim. Several self-citations appear (Franchini et al. 2023, Allievi et al. 2026, Kejriwal et al. 2024, Broggi et al. 2022), but in each case the same step is either supported by an external citation or is peripheral; the central conclusion would stand even if those self-citations were removed. Hence no specific circular step can be exhibited; score 2 reflects only minor, non-load-bearing self-citation and model dependence, not circularity.

Axiom & Free-Parameter Ledger

3 free parameters · 7 axioms · 0 invented entities

The central assessment rests on the EMRI-QPE hypothesis, the LISA sensitivity model, and the luminosity-based exclusion of compact secondaries. The new IMBH tension estimate additionally depends on three poorly constrained population parameters (f_disk, f_short_compl, R_m) and on grouping three sources into one population. No new physical entities are introduced.

free parameters (3)
  • f_disk = 10^-2 (generous), 10^-3, 10^-4
    Fraction of MBHs with a disk dense enough to fuel QPEs. This dominates the expected IMBH count in Eq. (15) and is inferred from uncertain TDE rates and disk lifetimes rather than measured.
  • f_short_compl = ≲0.45
    Short-period QPE survey completeness estimated by combining eROSITA completeness and serendipitous discoveries. Directly scales Λ in Eq. (15) and is acknowledged as hard to derive from first principles.
  • R_m (IMBH inspiral rate per host) = R_max ≈ 7e-8 yr^-1 host^-1
    Mean IMBH-MBH inspiral rate per host, set to the mass-growth upper bound in the 'generous' corner. The actual rate is unknown and could be much lower, which would tighten the tension further.
axioms (7)
  • domain assumption QPEs are produced by an EMRI secondary impacting an accretion disk around a massive black hole.
    The entire assessment is conditional on the leading EMRI hypothesis for QPEs; the paper states this in the Introduction and Section 3.
  • domain assumption LISA sensitivity and SNR thresholds follow the Robson et al. (2019) model, with EMRI SNR cutoffs of 15–20.
    The non-detectability conclusions depend on this assumed detector model and search cutoff.
  • domain assumption The QPE luminosity is blackbody emission from a region of radius R_char ≈ R_sun.
    Eq. (9) and the surrounding discussion use this to rule out compact-object secondaries, a load-bearing step for the population disparity.
  • standard math Leading-order Peters and Peters-Mathews formulas describe GW emission and period decay.
    Used throughout for period derivatives, SNR scalings, and inspiral times; this is standard accepted physics.
  • domain assumption Main-sequence stars are tidally disrupted before reaching the LISA band.
    Eqs. (11)–(12) and the dynamical-frequency argument exclude main-sequence secondaries from LISA, supporting the need for compact or IMBH secondaries.
  • ad hoc to paper The three short-period QPEs can be treated as a single IMBH-MBH population with the stated completeness.
    The paper groups eRO-QPE2, RX J1301.9+2747, and GSN 069 as one population; the authors justify this by similarity but it is a modeling choice.
  • standard math Wilks' theorem is applicable to the Poisson likelihood ratio for the significance Z in Eq. (16).
    The theorem is used to convert the likelihood ratio to a σ value, but its applicability near the Λ ≥ 0 boundary and with small counts is questionable.

pith-pipeline@v1.3.0-alltime-deepseek · 30554 in / 15816 out tokens · 170474 ms · 2026-08-01T23:35:06.760869+00:00 · methodology

0 comments
read the original abstract

Quasi-Periodic Eruptions (QPEs) are recurring soft X-ray transients that may be generated by inspirals of stellar-mass objects spiraling into supermassive black holes, known as extreme mass ratio inspirals (EMRIs). Independently, EMRIs and the gravitational-wave signals they generate are one of the key targets for the Laser Interferometer Space Antenna (LISA). What is the potential of a coincident detection of EMRIs both as a QPE and by LISA? Electromagnetic counterparts to LISA events would provide sky localization, enable standard siren measurements of the Hubble constant and constrain formation mechanisms of the corresponding inspirals. Combined observations would link the accurate measurements of black hole masses and spins to their galactic nuclear environments and would thus enable lasting synergies with various observations across the electromagnetic spectrum. However, most of the currently known QPEs imply EMRI orbital periods that place the frequencies of the corresponding gravitational-wave signal out of the LISA sensitivity band. Additionally, the selection biases of QPE detections and the LISA instrument may preclude a coincident detection. Future searches should focus on expanding the QPE catalogs and ultimately hunt for ``golden'' short-period QPEs that correspond to EMRIs that fall within the LISA band.

discussion (0)

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Reference graph

Works this paper leans on

15 extracted references · 6 linked inside Pith

  1. [1]

    G., Abouelfettouh, I., Acernese, F., et al

    Abac, A. G., Abouelfettouh, I., Acernese, F., et al. (2025). GWTC-4.0: An Introduc- tion to Version 4.0 of the Gravitational-Wave Transient Catalog.ApJ, 995(1):L18. Abbott, B. P., Abbott, R., Abbott, T. D., et al. (2017). A gravitational-wave standard siren measurement of the Hubble constant. Nature, 551(7678):85–88. Abramowicz, M. A. and Fragile, P. C. (...

    2025

  2. [4]

    Babak, S., Gair, J., Sesana, A., et al

    Classical and Quantum Gravity, 27(8):084009. Babak, S., Gair, J., Sesana, A., et al. (2017). Science with the space-based interfer- ometer LISA. V. Extreme mass-ratio inspirals. Phys. Rev. D, 95(10):103012. Babak, S., Hewitson, M., and Petiteau, A. (2021). LISA Sensitivity and SNR Calculations. arXiv e-prints, page arXiv:2108.01167. Baldry, I. K., Driver,...

    Pith/arXiv arXiv 2017

  3. [7]

    Martens, W., Khan, M., and Bayle, J.-B

    Oxford university press. Martens, W., Khan, M., and Bayle, J.-B. (2023). LISAmax: improving the low- frequency gravitational-wave sensitivity by two orders of magnitude. Classical and Quantum Gravity, 40(19):195022. Masterson, M., Kara, E., Panagiotou, C., et al. (2025). Millihertz oscillations near the innermost orbit of a supermassive black hole. Nature...

    2023

  4. [8]

    Jiang, N

    Princeton University Press. Jiang, N. and Pan, Z. (2025). Embers of Active Galactic Nuclei: Tidal Disruption Events and Quasiperiodic Eruptions. ApJ, 983(1):L18. Kara, E. and Garc´ıa, J. (2025). Supermassive Black Holes in X-Rays: From Standard Accretion to Extreme Transients. ARA&A, 63(1):379–430. Katz, M. L., Karnesis, N., Korsakova, N., et al. (2025). ...

    arXiv 2025

  5. [9]

    Miniutti, G., Giustini, M., Arcodia, R., et al

    A&A, 693:A179. Miniutti, G., Giustini, M., Arcodia, R., et al. (2023a). Alive and kicking: A new QPE phase in GSN 069 revealing a quiescent luminosity threshold for QPEs. A&A, 674:L1. Miniutti, G., Giustini, M., Arcodia, R., et al. (2023b). Repeating tidal disruptions in GSN 069: Long-term evolution and constraints on quasi-periodic eruptions’ models. A&A...

    Pith/arXiv arXiv 2019

  6. [10]

    Pan, Z., Lyu, Z., and Yang, H

    ApJ, 928(2):L18. Pan, Z., Lyu, Z., and Yang, H. (2021). Wet extreme mass ratio inspirals may be more common for spaceborne gravitational wave detection. Phys. Rev. D, 104(6):063007. Pan, Z. and Yang, H. (2021). Formation rate of extreme mass ratio inspirals in active galactic nuclei. Phys. Rev. D, 103(10):103018. Pankow, C., Sampson, L., Perri, L., et al....

    Pith/arXiv arXiv 2021

  7. [12]

    Robson, T., Cornish, N

    The Astrophysical Journal, 977(1):120. Robson, T., Cornish, N. J., and Liu, C. (2019). The construction and use of LISA sensitivity curves. Classical and Quantum Gravity, 36(10):105011. Schutz, B. F. (1989). Gravitational wave sources and their detectability. Classical and Quantum Gravity, 6(12):1761–1780. Schwarzenberg-Czerny, A. (1989). On the advantage...

    2019

  8. [35]

    G., Casertano, S., Yuan, W., et al

    Riess, A. G., Casertano, S., Yuan, W., et al. (2018). New Parallaxes of Galactic Cepheids from Spatially Scanning the Hubble Space Telescope: Implications for the Hubble Constant. ApJ, 855(2):136. Riess, A. G., Scolnic, D., Anand, G. S., et al. (2024). Jwst validates hst distance measurements: Selection of supernova subsample explains differences in jwst ...

    2018

  9. [69]

    Allievi, C

    A&A, 705:L13. Allievi, C. M., Broggi, L., Sesana, A., and Bonetti, M. (2026). Two-body relaxation in the EMRI-TDE disk model for Quasi Periodic Eruptions. arXiv e-prints, page arXiv:2603.02302. Amaro-Seoane, P., Andrews, J., Arca Sedda, M., et al. (2023). Astrophysics with the Laser Interferometer Space Antenna. Living Reviews in Relativity, 26(1):2. Amar...

    arXiv 2026

  10. [165]

    Sesana, A., Korsakova, N., Arca Sedda, M., et al. (2021). Unveiling the gravitational universe at𝜇-Hz frequencies. Experimental Astronomy, 51(3):1333–1383. Shakura, N. I. and Sunyaev, R. A. (1973). Black holes in binary systems. Observa- tional appearance. A&A, 24:337–355. Shvartzvald, Y., Waxman, E., Gal-Yam, A., et al. (2024). ULTRASAT: A Wide-field Tim...

    Pith/arXiv arXiv 2021

  11. [534]

    Peters, P. C. (1964). Gravitational radiation and the motion of two point masses. Phys. Rev., 136:B1224–B1232. Peters, P. C. and Mathews, J. (1963). Gravitational radiation from point masses in a keplerian orbit. Physical Review, 131(1):435. Pihajoki, P. (2016). Black hole accretion disc impacts.MNRAS, 457(2):1145–1161. Piovano, G. A., Brito, R., Maselli,...

    1964

  12. [960]

    and Loeb, A

    Stone, N. and Loeb, A. (2012). Observing Lense-Thirring Precession in Tidal Disruption Flares. Phys. Rev. Lett., 108(6):061302. Stone, N. C. and Metzger, B. D. (2016). Rates of stellar tidal disruption as probes of the supermassive black hole mass function. MNRAS, 455(1):859–883. Sukov´a, P., Zajaˇcek, M., Witzany, V., and Karas, V. (2021). Stellar Transi...

    arXiv 2012

  13. [1519]

    Belloni, T. M. and Stella, L. (2014). Fast Variability from Black-Hole Binaries. Space Sci. Rev., 183(1-4):43–60. Broggi, L., Bortolas, E., Bonetti, M., et al. (2022). Extreme mass ratio inspirals and tidal disruption events in nuclear clusters - I. Time-dependent rates. MNRAS, 514(3):3270–3284. Cao, C., Liu, F. K., Chen, X., and Li, S. (2025). Formation ...

    Pith/arXiv arXiv 2014

  14. [1832]

    Zhou, C., Zeng, Y., and Pan, Z. (2025b). Secular Evolution of Quasiperiodic Erup- tions. ApJ, 985(2):242. Zhou, C., Zhong, B., Zeng, Y., et al. (2024). Probing orbits of stellar mass ob- jects deep in galactic nuclei with quasiperiodic eruptions. II. Population analysis. Phys. Rev. D, 110(8):083019

    2024

  15. [1956]

    R., Babak, S., Sesana, A., et al

    Gair, J. R., Babak, S., Sesana, A., et al. (2017). Prospects for observing extreme- mass-ratio inspirals with LISA. In Journal of Physics Conference Series, volume 840 of Journal of Physics Conference Series, page 012021. IOP. Multimessenger prospects of quasi-periodic eruptions 33 Gair, J. R., Vallisneri, M., Larson, S. L., and Baker, J. G. (2013). Testi...

    Pith/arXiv arXiv 2017