SciPost Submission Page
Dancing in the dark: probing Dark Matter through the dynamics of eccentric binary pulsars
by Giorgio Nicolini, Andrea Maselli, Miguel Zilhão
Submission summary
| Authors (as registered SciPost users): | Andrea Maselli · Miguel Zilhão |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202601_00044v1 (pdf) |
| Date submitted: | Jan. 19, 2026, 5:41 p.m. |
| Submitted by: | Miguel Zilhão |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
|
| Approach: | Theoretical |
Abstract
We investigate the dynamics of eccentric binary pulsars embedded in dark matter environments. While previous studies have primarily focused on circular orbits in collisionless dark matter halos, we extend this framework to eccentric systems and explore their interaction with ultralight scalar fields. Adopting a perturbative approach, we compute the modifications to the orbital period induced by dark matter-driven dynamical friction. Our results show that orbital eccentricity amplifies the imprints of non-vacuum environments on binary dynamics, underscoring the potential of such systems as sensitive probes for dark matter signatures.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
Reply to Referee Report on Manuscript 2507.16904 "Dancing in the dark: probing Dark Matter through the dynamics of eccentric binary pulsars"
Dear Editor,
we thank the referee for their careful reading of our manuscript and for their insightful comments and suggestions. We address each point below and have revised the manuscript accordingly.
OVERALL COMMENTS
[MAJOR] Comment 1: Figures too small
Referee: "The figures are too small, which makes their content difficult to read; I recommend enlarging them for clarity."
Reply: We appreciate this observation and have enlarged all figures and corresponding fonts in the revised manuscript.
[MINOR] Comment 2: Local DM density clarification
Referee: "The Introduction (and subsequent sections) states that 'the local DM density in the Milky Way halo is typically 0.3 ± 0.1 GeV cm−3.' To avoid ambiguity, the authors should clarify that this value refers to the local density in the Solar neighborhood."
Reply: We have revised the text to explicitly state that this refers to the local density in the Solar neighborhood.
INTRODUCTION
[MINOR] Comment 3: Literature review - gravitational vs. non-gravitational probes
Referee: "The literature review would benefit from a clearer distinction between studies addressing purely gravitational probes of dark matter and those invoking non-gravitational (direct) couplings. For instance, Refs. 24 and 26 predict significant observable effects only in the presence of direct scalar couplings. To strengthen the Introduction, it would be useful if the authors also highlighted the works (if these exist) that focus exclusively on gravitational effects and predict potentially observable signatures in pulsar binaries."
Reply: We thank the referee for this suggestion. We have revised the Introduction to more clearly make this distinguish and emphasize that our work focuses on purely gravitational effects (cf. the paragraph starting with "Herein, we will focus exclusively on gravitational drag effects, without assuming any direct coupling between DM and the binary constituents").
DYNAMICAL EVOLUTION OF BINARY PULSARS
[MAJOR] Comment 4: Missing de/df contribution in Eq. (9)
Referee: "In arriving at Eq. (9) from dp/df and Kepler's third law, there should be a contribution of de/df; in particular, this includes a term in the radial component of the force R. Could the authors clarify why does it not appear in Eq. (9)?"
Reply: We thank the referee for noticing this. It was indeed an oversight on our part. We have now included the de/df contribution in Eq. (9) and corrected the expression accordingly. This correction affects the subsequent plots and results, in some cases with significant changes. We have therefore redone all plots and modified the corresponding discussion in the revised manuscript. Sections 4 and 5 have therefore been substantially updated to reflect these changes.
[MAJOR] Comment 5: Validity condition for Eq. (27)
Referee: "Just after Eq. (27): 'the expression (26) is valid only...'. It should be the opposite of what is written. Eq. (27) is valid when the de Broglie wavelength is much smaller than the cutoff radius (the semi-minor axis, in this case). For binary pulsars with Pb ≈ 100 days, the separation is ∼ 10^11 m. This is smaller than most of the Compton wavelengths considered in Fig. 5, and much smaller than the corresponding de Broglie wavelengths. This suggests that Eq. (27) is being applied outside of its regime of validity. Could the authors clarify that?"
Reply: The referee is indeed correct, we had made a mistake in the statement regarding the validity condition. We have replaced equation (27) with the expression that is valid in both regimes. With this change the new results show that the effects are generally smaller than previously estimated, so we have adapted the text accordingly.
[MINOR] Comment 6: Coulomb logarithm value
Referee: "The manuscript adopts a Coulomb logarithm value of λ ≈ 20. Could the authors clarify the origin of this estimate? Is the implicit choice of bmax consistent with what is used later in Eq. 25? A short discussion or citation would help the reader understand the basis for this choice and ensure consistency across the analysis."
Reply: We use the choice of λ ≈ 20 following standard practice in the literature; we have added footnote 1 to make this clear.
CHANGES IN THE ORBITAL PERIOD DUE TO DARK MATTER
[MINOR] Comment 7: Unclear statements about vw and σ effects
Referee: "At the end of p. 8, the statements 'increasing vw for fixed σ generally leads to slightly higher Ṗb' and 'variations in σ for fixed vw have a subtler effect' are unclear, since Fig. 1 appears to shows the opposite trend."
Reply: This text has now been revised with the newer results.
[MINOR] Comment 8: Physical mechanism for positive Ṗb
Referee: "The authors state that Ṗb is positive both for ultralight dark matter and for certain regions of parameter space in the collisionless dark matter case. This seems counter-intuitive, as one would generally expect dynamical friction to produce orbital decay. Could the authors elaborate on the physical mechanism underlying this behavior? The manuscript would benefit from a brief discussion of this point."
Reply: This text has also been revised with the newer results.
FINAL REMARKS
[MAJOR] Comment 9: Observational sensitivity to Ṗb
Referee: "The authors present estimates for the order of magnitude of the effects studied here and compare them with orbital decay from gravitational-wave emission. However, the discussion does not mention the typical sensitivity of current (or planned) pulsar timing observations to Ṗb. Including this would help the reader assess the observational relevance of the predicted effects."
Reply: This is indeed a very important point. We have expanded the discussion section and added references on this. We note, however, that we were not able to find in the literature explicit numbers for the sensitivity to Ṗb in the planned pulsar timing observations.
List of changes
Warnings issued while processing user-supplied markup:
- Inconsistency: Markdown and reStructuredText syntaxes are mixed. Markdown will be used.
Add "#coerce:reST" or "#coerce:plain" as the first line of your text to force reStructuredText or no markup.
You may also contact the helpdesk if the formatting is incorrect and you are unable to edit your text.
============================================================================== SUMMARY OF CHANGES ==============================================================================
In summary, we have made the following changes to the manuscript:
MAJOR CHANGES:
-
Corrected Eq. (9) to include the missing de/df contribution involving the radial force component R. This is a critical correction that affects all subsequent calculations.
-
Replaced Eq. (27) with a new expression, correcting the previously stated validity condition.
-
Updated all figures (Figs. 1-4) with new results reflecting the corrected equations. The figures have also been enlarged for better readability.
-
Substantially revised Sections 4 to reflect the corrected calculations and updated numerical results.
-
Expanded the final remarks section (Section 5).
MINOR CHANGES:
-
Clarified in the Introduction that the local DM density value (0.3 ± 0.1 GeV cm^-3) refers specifically to the Solar neighborhood.
-
Reorganized and expanded the Introduction to clearly distinguish between:
- Studies focused on purely gravitational effects
-
Studies involving non-gravitational (direct) couplings Added explicit statement that this work focuses exclusively on gravitational drag effects.
-
Added footnote 1 explaining the choice of Coulomb logarithm λ ≈ 20, noting it follows standard literature practice.
-
Corrected minor typos.
Current status:
Reports on this Submission
Report
As motivated in the first report, in my opinion the manuscript can be published in its current form.
Optionally, I notice that the bottom panel of Fig.1 lacks the vertical scale. The horizontal line compensate for this, but this looks like a nonstandard choice.
Recommendation
Publish (surpasses expectations and criteria for this Journal; among top 10%)
Report
Nevertheless, I am happy to recommend the manuscript for publication in SciPost in its present form.
Recommendation
Publish (easily meets expectations and criteria for this Journal; among top 50%)