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Probing Direct Waves in Black Hole Ringdowns

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arxiv 2509.09165 v1 pith:P5GOB2Q5 submitted 2025-09-11 gr-qc

Probing Direct Waves in Black Hole Ringdowns

classification gr-qc
keywords blackwavedirectholefrequencygravitationalwavescurrent
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Merger gravitational waves from binary black hole coalescence carry rich information about the underlying spacetime dynamics. We analyze merger waves from comparable-mass and extreme-mass-ratio binaries, obtained from numerical relativity and black-hole perturbation theory, respectively, and argue that they are dominated by the prompt wave emissions as the black holes collide. This signal, which we refer to as the direct wave, is modulated by the plunging motion and selectively screened by the gravitational potential of the remnant black hole. The direct wave typically exhibits a time-dependent frequency and decay rate, but for high-spin remnants $(\gtrsim0.7)$ the ergosphere renders it mode-like, with a quasi-stable instantaneous oscillation frequency close to the superradiant frequency. We further estimate its detectability in a GW150914-like system and find that the signal-to-noise ratio can exceed $\sim 10$ with the current ground-based detector network. Our results therefore identify the direct wave as a robust observable for analyzing black hole ringdowns in current and future gravitational wave events.

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Forward citations

Cited by 13 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Foundations of Direct Waves in Schwarzschild Ringdown

    gr-qc 2026-07 accept novelty 7.0

    Direct waves in filtered Schwarzschild ringdown are the anti-causal filter-pole contribution sourced by near-horizon trajectory dynamics and do not vanish.

  2. The Direct Wave is Not a Meaningful Test of Horizon Properties

    gr-qc 2026-07 accept novelty 7.0

    Numerical relativity analysis shows the direct wave frequency in binary black hole mergers correlates with horizon frequency only incidentally at χ_f ≈ 0.7 and has evolving damping time, making it unsuitable as a prob...

  3. Vanishing of all redshift modes in Schwarzschild ringdown

    gr-qc 2026-06 unverdicted novelty 7.0

    All redshift-mode contributions to Schwarzschild black-hole ringdown waveforms vanish exactly because causality forces the source-integrated Green function to vanish on the light cone.

  4. Measuring a Black Hole's Area Immediately after Merger: A Direct-Wave Test of Hawking's Area Law

    gr-qc 2026-06 unverdicted novelty 7.0

    A gravitational-wave method infers the Kerr-equivalent horizon area from direct waves in the near-merger signal of GW250114, yielding consistency with the Kerr remnant and a new test of Hawking's area law.

  5. Calculation of a regularized Teukolsky Green function in Schwarzschild spacetime

    gr-qc 2026-04 unverdicted novelty 7.0

    Exact expressions are obtained for the direct singular part of the Teukolsky retarded Green function in Schwarzschild spacetime, including angular factors and spin-dependent transport terms for constant-radius orbits.

  6. Early metal-enriched baryon cycling before the midpoint of cosmic reionization

    astro-ph.GA 2026-04 conditional novelty 7.0

    Blueshifted metal absorption lines in three z=7.2-9.3 galaxies indicate that metal-enriched, kinematically disturbed gas was already present around galaxies before the midpoint of cosmic reionization.

  7. Pole Structure of Kerr Green's Function

    gr-qc 2026-05 unverdicted novelty 6.0

    Homogeneous solutions and connection coefficients in the radial Teukolsky equation for Kerr black holes exhibit simple poles at Matsubara frequencies that cancel in the Green's function, along with canceling zero-freq...

  8. Early metal-enriched baryon cycling before the midpoint of cosmic reionization

    astro-ph.GA 2026-04 conditional novelty 6.0

    The direct Hadamard term for the Teukolsky Green function in Schwarzschild is factored into closed-form S² and exact M² components, enabling regularized ℓ-mode calculations for spin-1 and spin-2 perturbations.

  9. Dynamical quasinormal mode excitation II: propagation and convergence in Schwarzschild

    gr-qc 2026-05 unverdicted novelty 5.0

    Refined propagation prescription for quasinormal modes excited by plunging particles confirms a bounce radius at r_*=0 and yields accurate reproduction of the post-bounce oscillatory waveform component from first principles.

  10. Ringdown Analysis of GW250114 with Orthonormal Modes

    gr-qc 2026-05 unverdicted novelty 5.0

    Orthonormal QNM analysis of GW250114 raises the significance of the first overtone of the ℓ=m=2 mode from 82.5% to 99.9% and detects no significant deviation from Kerr predictions.

  11. Prompt Response from Plunging Sources in Schwarzschild Spacetime

    gr-qc 2026-04 unverdicted novelty 5.0

    The prompt response is ~1.2 times stronger than quasinormal mode excitation during inspiral and enables 99% accurate reconstruction of the full inspiral-merger-ringdown waveform when combined with other components.

  12. Green function of the P\"{o}schl-Teller potential

    gr-qc 2025-10 unverdicted novelty 5.0

    Exact time-domain Green function computed for the Pöschl-Teller approximation to black-hole perturbation potentials, revealing additional early-time exponentially growing modes and a light-cone plus historical wavefor...

  13. Modeling Direct Waves in Binary Black Hole Ringdowns

    gr-qc 2026-06 unverdicted novelty 4.0

    Direct waves are identified in NR ringdown waveforms using QNM extraction techniques over a range of start times, but their frequency deviates from the horizon-mode prediction.