REVIEW
Measuring gravitational waves from binary black hole coalescences: I. Signal to noise for inspiral, merger, and ringdown
General Relativity and Quantum Cosmology · Submitted 16 Jan 1997 · 103 references
Pith's verdict: A foundational, largely honest SNR survey whose headline mass thresholds are softer than the confident framing suggests.
T0 · AI review
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Referee report
The paper
The paper claims
For heavy black holes, the merger outshouts the chirp
The reading
What carries the argument
The load-bearing object is the angle-averaged matched-filter signal-to-noise identity, Eq. (2.34): $4$-normalized optimal filtering squared, averaged over source orientation and position, equals a frequency integral of the source's emitted energy spectrum $dE_e/df_e$ evaluated at the redshifted frequency $(1+z)f$, weighted by $1/(f^2 S_h(f))$ and scaled by $(1+z)^2/D(z)^2$. Its virtue is that the answer depends only on the energy spectrum, not on the detailed waveform or the geometry of the source relative to the detector, so the three phases can be compared on a single footing. Feeding in three model spectra — the Newtonian quadrupole inspiral spectrum cut off at $f=0.02/M$, a flat merger spectrum from $0.02/M$ to $0.13/M$ carrying 10 percent of the mass-energy, and a Breit-Wigner ringdown resonance at the $l=m=2$ quasinormal frequency with 3 percent of the mass-energy — against piecewise power-law fits to the detector noise curves produces the mass-dependent signal-to-noise curves that drive every conclusion. A second piece of machinery is the template-counting metric on the two-dimensional ringdown parameter space of frequency and quality factor, which yields the estimate of roughly 6000 templates for a 10 percent event-rate loss.
Extended reading notes
Core claim
The paper establishes a mass-dependent rule for how binary black hole coalescences should be searched for. Using an angle-averaged optimal-filtering signal-to-noise ratio, it shows that the inspiral phase dominates only for relatively light systems, while the merger and ringdown phases take over above roughly $(1+z)M$ of about $30M_*$ for the initial interferometers and about $60M_*$ for the advanced ones, with the inspiral contribution cutting off entirely near $100M_*$ and $410M_*$ respectively once its whole spectrum falls below the seismic wall. The authors then turn that into concrete reach estimates: a matched-filter ringdown search needs only about 6000 templates or fewer and should find equal-mass systems of roughly $100$ to $700M_*$ out to about 200 Mpc with initial interferometers, $200$ to $3000M_*$ out to $z$ near 1 with advanced ones, and $10^6$ to $3$ times $10^8M_*$ out to $z$ beyond 100 with LISA. Finally, they argue that a nonlinear noise-monitoring search for merger waves, which needs no detailed waveform knowledge, could raise the number of detected massive binaries by a factor of order ten, with a complete set of numerical-relativity merger templates adding at most another factor of about four.
Load-bearing premise
The merger signal-to-noise numbers, and the headline factor-of-ten gain from merger searches, rest on a chosen flat merger energy spectrum carrying 10 percent of the total mass-energy, a value the authors themselves describe as a reasonable upper bound achievable in favorable cases rather than a best guess.
Editorial extensions
If this is right
- A search pipeline built exclusively around the inspiral chirp will systematically miss equal-mass binaries above roughly 30 solar masses for initial interferometers and 60 for advanced ones, because their signal-to-noise is carried by the merger and ringdown instead.
- Ringdown searches are practical now rather than in some future: the template bank is small compared with inspiral banks, and the waveform family is known analytically from Kerr perturbation theory.
- Coalescing black holes, not neutron-star binaries, may be the first gravitational-wave sources detected, because their larger mass buys a distance gain that plausibly outweighs a lower event rate.
- Even without any merger waveform templates, a nonlinear noise-monitoring statistic can recover a large share of the massive binaries that template searches would miss, so the unknown merger waveform is not a hard barrier to detection.
- LISA would measure supermassive black hole coalescences with signal-to-noise of order $10^4$, high enough that the merger and ringdown phases are visible essentially throughout the observable universe.
Reading between the lines
- The mass-dependent search-phase rule is a statement about where the signal-to-noise lives, not about where the physics is best understood; it implies a trade between detection reach and interpretability that later observing strategy has to make explicitly.
- Because the ringdown frequency and damping time map one-to-one onto final mass and spin, a ringdown detection is simultaneously a measurement of the remnant, so the ringdown search doubles as a black-hole census instrument rather than only a trigger.
- The paper's own logic suggests the reverse search problem is worth stating: given a detected ringdown with no inspiral counterpart, the absence of inspiral signal above the seismic cutoff itself constrains the total mass, which is a consistency check that needs no merger templates.
- The noise-monitoring statistic is essentially an incoherent power sum over frequency bins, so its advantage shrinks as the number of independent bins grows; this predicts that any future waveform family richer than the merger's roughly 10 to 60 bins would erode the factor-of-ten gain claimed here.
Original abstract
We estimate the expected signal-to-noise ratios (SNRs) from the three phases (inspiral,merger,ringdown) of coalescing binary black holes (BBHs) for initial and advanced ground-based interferometers (LIGO/VIRGO) and for space-based interferometers (LISA). LIGO/VIRGO can do moderate SNR (a few tens), moderate accuracy studies of BBH coalescences in the mass range of a few to about 2000 solar masses; LISA can do high SNR (of order 10^4) high accuracy studies in the mass range of about 10^5 to 10^8 solar masses. BBHs might well be the first sources detected by LIGO/VIRGO: they are visible to much larger distances (up to 500 Mpc by initial interferometers) than coalescing neutron star binaries (heretofore regarded as the "bread and butter" workhorse source for LIGO/VIRGO, visible to about 30 Mpc by initial interferometers). Low-mass BBHs (up to 50 solar masses for initial LIGO interferometers; 100 for advanced; 10^6 for LISA) are best searched for via their well-understood inspiral waves; higher mass BBHs must be searched for via their poorly understood merger waves and/or their well-understood ringdown waves. A matched filtering search for massive BBHs based on ringdown waves should be capable of finding BBHs in the mass range of about 100 to 700 solar masses out to 200 Mpc (initial LIGO interferometers), and 200 to 3000 solar masses out to about z=1 (advanced interferometers). The required number of templates is of order 6000 or less. Searches based on merger waves could increase the number of detected massive BBHs by a factor of order 10 or more over those found from inspiral and ringdown waves, without detailed knowledge of the waveform shapes, using a "noise monitoring" search algorithm. A full set of merger templates from numerical relativity could further increase the number of detected BBHs by an additional factor of up to 4.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
We estimate the expected signal-to-noise ratios (SNRs) from the three phases (inspiral,merger,ringdown) of coalescing binary black holes (BBHs) for initial and advanced ground-based interferometers (LIGO/VIRGO) and for space-based interferometers (LISA). LIGO/VIRGO can do moderate SNR (a few tens), moderate accuracy studies of BBH coalescences in the mass range of a few to about 2000 solar masses; LISA can do high SNR (of order 10^4) high accuracy studies in the mass range of about 10^5 to 10^8 solar masses. BBHs might well be the first sources detected by LIGO/VIRGO: they are visible to much larger distances (up to 500 Mpc by initial interferometers) than coalescing neutron star binaries (heretofore regarded as the "bread and butter" workhorse source for LIGO/VIRGO, visible to about 30 Mpc by initial interferometers). Low-mass BBHs (up to 50 solar masses for initial LIGO interferometers; 100 for advanced; 10^6 for LISA) are best searched for via their well-understood inspiral waves; higher mass BBHs must be searched for via their poorly understood merger waves and/or their well-understood ringdown waves. A matched filtering search for massive BBHs based on ringdown waves should be capable of finding BBHs in the mass range of about 100 to 700 solar masses out to 200 Mpc (initial LIGO interferometers), and 200 to 3000 solar masses out to about z=1 (advanced interferometers). The required number of templates is of order 6000 or less. Searches based on merger waves could increase the number of detected massive BBHs by a factor of order 10 or more over those found from inspiral and ringdown waves, without detailed knowledge of the waveform shapes, using a "noise monitoring" search algorithm. A full set of merger templates from numerical relativity could further increase the number of detected BBHs by an additional factor of up to 4.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We estimate the expected signal-to-noise ratios (SNRs) from the three phases (inspiral,merger,ringdown) of coalescing binary black holes (BBHs) for initial and advanced ground-based interferometers (LIGO/VIRGO) and for space-based interferometers (LISA). | contribution 1.00 | 0.89 | 0.13 | asserted 0.91 |
| s1 | LIGO/VIRGO can do moderate SNR (a few tens), moderate accuracy studies of BBH coalescences in the mass range of a few to about 2000 solar masses; LISA can do high SNR (of order 10^4) high accuracy studies in the mass range of about 10^5 to 10^8 solar masses. | result 0.95 | 0.72 | 0.32 | asserted 0.88 |
| s2 | BBHs might well be the first sources detected by LIGO/VIRGO: they are visible to much larger distances (up to 500 Mpc by initial interferometers) than coalescing neutron star binaries (heretofore regarded as the "bread and butter" workhorse source for LIGO/VIRGO, visible to about 30 Mpc by initial interferometers). | result 0.49 | 0.28 | 0.11 | hedged possibility 0.49 |
| s3 | Low-mass BBHs (up to 50 solar masses for initial LIGO interferometers; 100 for advanced; 10^6 for LISA) are best searched for via their well-understood inspiral waves; higher mass BBHs must be searched for via their poorly understood merger waves and/or their well-understood ringdown waves. | result 0.70 | 0.54 | 0.11 | asserted 0.95 |
| s4 | A matched filtering search for massive BBHs based on ringdown waves should be capable of finding BBHs in the mass range of about 100 to 700 solar masses out to 200 Mpc (initial LIGO interferometers), and 200 to 3000 solar masses out to about z=1 (advanced interferometers). | result 0.99 | 0.67 | 0.13 | hedged possibility 0.95 |
| s5 | The required number of templates is of order 6000 or less. | result 0.96 | 0.74 | 0.07 | asserted 0.99 |
| s6 | Searches based on merger waves could increase the number of detected massive BBHs by a factor of order 10 or more over those found from inspiral and ringdown waves, without detailed knowledge of the waveform shapes, using a "noise monitoring" search algorithm. | result 0.88 | 0.42 | 0.15 | hedged possibility 0.99 |
| s7 | A full set of merger templates from numerical relativity could further increase the number of detected BBHs by an additional factor of up to 4. | result 0.60 | 0.35 | 0.10 | hedged possibility 0.94 |
What was examined, and what was not
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Figures
Figures reproduced from arXiv:gr-qc/9701039 by the authors.
References
How later papers used it
134 later papers cite it
8 later papers by other authors are listed below: 8 used its method or tool.
Uses its method or tool 8 of 52 papers with this label
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Computed the SNR accumulated over the observational time following this paper's formalism.
Probing $z \gtrsim 6$ massive black holes with gravitational waves (2023) · 0.99 · paraphrased: the licence does not allow quoting
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Calculated the characteristic GW strain for a given frequency using this paper.
Gravitational Wave Signatures of Ab Initio Two-Dimensional Core Collapse Supernova Explosion Models for 12-25 Solar Masses Stars (2015) · 0.99 · paraphrased: the licence does not allow quoting
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We use [https://legwork.readthedocs.io] [ref] to determine the detectability of our simulated DWD populations for sources with GW frequencies $f_GW>10^-4 Hz$. calculates the position-, orientation-, and angle-averaged signal to noise ratio (SNR) for inspiraling GW sources closely following the derivations of [ref] and using the LISA noise power spectral density (PSD) of [ref] .
Applying the metallicity-dependent binary fraction to double white dwarf formation: Implications for LISA (2021) · LISA detectability · 1.00
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Calculated the position-, orientation-, and angle-averaged SNR for a circular binary system following this paper and another work.
Massive Double White Dwarf Binary Mergers from the Moon: Extending the Reach of Multi-messenger Astrophysics (2025) · 0.99 · paraphrased: the licence does not allow quoting
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Crudely estimated the signal to noise ratio of this characteristic strain for DECIGO using this paper.
Gravitational wave signals in the deci-Hz range from neutrinos during the proto-neutron star cooling phase (2022) · 0.98 · paraphrased: the licence does not allow quoting
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Took the factors within the minimum functions because each signal is only accumulated within its own lifetime or the LISA observation timescale, following this paper.
Gravitational-Wave Signatures from Compact Object Binaries in the Galactic Center (2020) · 0.83 · paraphrased: the licence does not allow quoting
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Used the signal-to-noise ratio for a matched filtered signal, citing this paper as an example, to roughly assess detectability of the GW signals.
Gravitational waves from three-dimensional core-collapse supernova models: The impact of moderate progenitor rotation (2018) · 1.00 · paraphrased: the licence does not allow quoting
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Calculated the single-detector SNR of the GW waveforms assuming the optimal orientation using this paper's Eq. (1.1).
Gravitational-wave Signature of a First-order Quantum Chromodynamics Phase Transition in Core-Collapse Supernovae (2020) · 1.00 · paraphrased: the licence does not allow quoting
How the literature uses it
77 arXiv papers cite this in 111 sentences
Papers citing it · 59 sentences without a confident label
Contests it 1 paper
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This is essentially the approach followed by Thorne [ref] , who examined the Christodoulou memory from unmodeled GW bursts from merging BHs.[Note that Thorne's [ref] normalization of the SNR should be corrected by multiplying his Eq. (A1) by $√(2)$ (see footnote 61 of Ref. [ref] ).] However the ZFL is inadequate for computing the memory's SNR for some sources.
Post-Newtonian corrections to the gravitational-wave memory for quasicircular, inspiralling compact binaries · Detecting memory with gravitational-wave interferometers · contest 0.77
Uses its method or tool 29 papers
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In order to determine the detectability of the GWs, we calculate the characteristic GW strain for a given frequency $f$ [ref] using [equation] [equation] where $dE_GW(f)/df$ is the GW energy spectrum and $Ã_20(f)$ denotes the Fourier transform of $A_20(t)$: [equation] The stochastic nature of GW signals from CCSNe prompts the use of short-time Fourier transform (STFT) techniques to determine the frequency of a signal as it changes over time [ref] : [equation] where $H(t - τ)$ is the Hann window function [ref] .
Gravitational Wave Signatures of Ab Initio Two-Dimensional Core Collapse Supernova Explosion Models for 12-25 Solar Masses Stars · GWs Produced by a Time-Dependent, Mass-Quadrupole Moment · 0.99
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To understand the impact of such energy loss on GW signals, we add to the quadrupole formula the energy flux [ref], and compute the correction to the GW phase in the stationary approximation [ref] .
Stirred and shaken: dynamical behavior of boson stars and dark matter cores · Introduction · 0.93
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For an optimally oriented detector the matched-filtering SNR squared, averaged over all possible source orientations is [ref]
On the dynamical bar-mode instability in spinning bosonic stars · Detectability · 0.89
Uses its data or values 3 papers
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As estimated in Ref. [ref] , the maximum value of $𝒜$ is taken to be $𝒜=0.4$.
Measuring the Black Hole Mass Spectrum from Redshifts of aLIGO Binary Merger Events · Detectability based on aLIGO · 0.97
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The values can range between $ϵ_rd∼0.8%-3%$ [ref] depending on the binary mass ratio and spins.
Generation and propagation of nonlinear quasi-normal modes of a Schwarzschild black hole · Importance of nonlinearities · 0.95
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Flanagan and Hughes [ref] argue that $E ∼0.03 (4ν)^2 M$.
Physics, Astrophysics and Cosmology with Gravitational Waves · Quasi-normal modes of a black hole · 0.93
Cites it as background 12 papers
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The QNM amplitudes $A_ℓm n$ and phases $ϕ_ℓm n$ were unknown before the first numerical BH merger simulations, and early work on BH spectroscopy [ref] had to rely on educated guesses [ref] .
Analysis of Ringdown Overtones in GW150914 · Introduction · 0.90
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The inspiral waveform measured in a gravitational wave detector is of the form of [ref] h(t) = h_0(t) cosϕ(t), where h_0(t)=4 Q/D_L G Mη Ω^2 r^2 and ϕ(t) = ∫2πf dt, with $D_L$ being the luminosity distance to the source and where $Q$ encodes the detector response as a function of the angular position and orientation of the binary.
Prospects for axion searches with Advanced LIGO through binary mergers · Waveform · 0.84
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With the emergence of GW astronomy, we now know that low-mass IMBH can form and grow through mergers with other BH[The term IMBH first began to appear in published papers from the late 1990s that were predicting the type of merging BH that could potentially be observed with future GW missions [ref] .]
Intermediate-Mass Black Holes in Star Clusters and Dwarf Galaxies · Context and definition · 0.87
Discussion
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