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Stringent Constraints on Gravitational Wave Signatures of Dark Electromagnetism in Neutron Star Binaries

Ian Harris, Yonatan Kahn

TL;DR

This work assesses whether a long-range dark vector force (dark electromagnetism) between neutron stars could imprint measurable gravitational-wave signatures. By combining gravitational-stability bounds, ambient DM accretion limits, self-capture dynamics, extreme galactic overdensities, and thermal production with fifth-force constraints, the authors show that the maximum GW signal strength $S$ is bounded by the DM mass fraction within NSs, typically yielding $S \lesssim 10^{-13}$ for local densities and $S \lesssim 10^{-8}$ under thermal-production scenarios. Although central galactic overdensities could in principle enhance the signal, dynamical processes likely erase such spikes, keeping realistic $S$ well below detectability. Neutron-decay channels with long-range forces face significant model-building constraints, further supporting the conclusion that dark EM signatures in NS binaries are unlikely to be observable with current or near-future GW detectors.

Abstract

Gravitational wave interferometers have studied compact object mergers and solidified our understanding of strong gravity. Their increasing precision raises the possibility of detecting new physics, especially in a neutron star binary system that may contain hidden-sector particles. In particular, a new vector force between binary constituents, giving rise to dark electromagnetic phenomena, could measurably alter the inspiral waveforms and thus be constrained by gravitational wave observations. In this work, we critically examine the mechanisms for neutron stars to acquire enough hidden-sector particles with requisite couplings to furnish a detectable signature from dark electromagnetism. We demonstrate that the repulsive nature of vector forces imposes stringent constraints on any putative particle physics model or astrophysical environment which could give rise to such gravitational signatures. We argue that absent an extreme fine-tuning of parameters, such signatures are well out of reach of any current or near-future gravitational wave observatory.

Stringent Constraints on Gravitational Wave Signatures of Dark Electromagnetism in Neutron Star Binaries

TL;DR

This work assesses whether a long-range dark vector force (dark electromagnetism) between neutron stars could imprint measurable gravitational-wave signatures. By combining gravitational-stability bounds, ambient DM accretion limits, self-capture dynamics, extreme galactic overdensities, and thermal production with fifth-force constraints, the authors show that the maximum GW signal strength is bounded by the DM mass fraction within NSs, typically yielding for local densities and under thermal-production scenarios. Although central galactic overdensities could in principle enhance the signal, dynamical processes likely erase such spikes, keeping realistic well below detectability. Neutron-decay channels with long-range forces face significant model-building constraints, further supporting the conclusion that dark EM signatures in NS binaries are unlikely to be observable with current or near-future GW detectors.

Abstract

Gravitational wave interferometers have studied compact object mergers and solidified our understanding of strong gravity. Their increasing precision raises the possibility of detecting new physics, especially in a neutron star binary system that may contain hidden-sector particles. In particular, a new vector force between binary constituents, giving rise to dark electromagnetic phenomena, could measurably alter the inspiral waveforms and thus be constrained by gravitational wave observations. In this work, we critically examine the mechanisms for neutron stars to acquire enough hidden-sector particles with requisite couplings to furnish a detectable signature from dark electromagnetism. We demonstrate that the repulsive nature of vector forces imposes stringent constraints on any putative particle physics model or astrophysical environment which could give rise to such gravitational signatures. We argue that absent an extreme fine-tuning of parameters, such signatures are well out of reach of any current or near-future gravitational wave observatory.

Paper Structure

This paper contains 12 sections, 24 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Gravitational stability constraints
  3. Accretion
  4. Geometric capture
  5. Accretion loopholes
  6. DM Self-Accretion Timescale
  7. Galactic Central Overdensity
  8. Thermal Production
  9. Model construction
  10. GW signal constraints
  11. Neutron Decay
  12. Conclusion

Figures (2)

  • Figure 1: Experimental constraints taken from Wagner_2012Berg__2022Kapner_2007 and adjusted to show the excluded region in terms of the gauge coupling and boson mass. Solid lines show fifth force constraints; the dashed line shows the limit from supernova bremsstrahlung production.
  • Figure 2: Maximum GW signal as a function of $B-L$ gauge boson mass $m_{B-L}$, for the thermal production scenario. The vertical dashed line marks where $m_{B-L}=R_*^{-1}$, where the mean-field calculation is no longer valid and the $B-L$ force is effectively long-ranged.