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Detecting gravitational-wave memory with LIGO-Virgo-KAGRA

Paul Lasky

Image: Carl Knox

displacement

^

with Eric Thrane, Moritz Huebner, Isobel Romero-Shaw, Shun Cheung, Colm Talbot

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Floor Broekgaarden

You are here!

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Not to scale...

  • Rule of thumb: memory amplitude ~1/20th oscillatory amplitude
  • Too small to measure with LIGO-Virgo-KAGRA
  • Memory SNR of GW150914 at design sensitivity ~ 0.42 

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What do we actually see?

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"stacking"

Lasky+2016

In 2016, we thought all events were as loud as GW150914

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"stacking"

Lasky+2016

In 2016, we thought all events were as loud as GW150914

Memory sign not known �S/N = 0

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All bow to the mighty Bayes

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Bayesian model selection

Evidence for a model

Likelihood of data h given model with parameters ξ

Prior probability of parameters ξ

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Bayesian model selection

, mem

, no mem

BF = 

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"stacking"

Lasky+2016

In 2016, we thought all events were as loud as GW150914

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Gravitational-wave memory: �observational status

… and �THE 

GOOD

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Adapted from Huebner, PL, & Thrane 2021

up to end of O3a; �analysis for O3b �to appear shortly

(Cheung+)

Moritz Huebner

Shun Cheung

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Adapted from Huebner, PL, & Thrane 2021

Huebner, Talbot,�PL, & Thrane 2020

Boersma, Nichols �& Schmidt 2020

Grant & Nichols 2023

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Floor Broekgaarden

You are here!

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Floor Broekgaarden

You are here!

Grant & Nichols 2023

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Many challenges; some in our control ...

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Many challenges; some in our control ...

Waveforms - I

Thorne 1992:

Implemented in Talbot, Thrane, PL & Liu 2018: GWMemory

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Many challenges; some in our control ...

BMS balance laws

Mitman+2021; Liu, He & Cao 2021.  Consistent enough (!?)

Waveforms - I

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Many challenges; some in our control ...

Waveforms - II

GW190521

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Many challenges; some in our control ...

Waveforms - II

Abbott+2020

  • Quasi-circular waveforms
  • Evidence of precession
  • Suggests dynamical formation
  • Second-generation merger?

​

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Many challenges; some in our control ...

Waveforms - II

Abbott+2020

  • Quasi-circular waveforms
  • Evidence of precession
  • Suggests dynamical formation
  • Second-generation merger?

​

Romero-Shaw, PL+2020

"… the data prefer a signal with eccentricity e > 0.1 at 10 Hz to a non-precessing, quasi-circular signal..."

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Many challenges; some in our control ...

Waveforms - II

  • Precession and eccentricity can be confused
    • (see e.g., Romero-Shaw, PL+2021,2022; Romero-Shaw, Gerosa, Loutrel 2023...)�
  • Waveforms for parameter estimation with precession and eccentricity don't exist
    • (see e.g., Gayathri+2022)�
  • We don't know the effect of these waveform systematics on our ability to measure memory...

Words of caution:

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Many challenges; some in our control ...

Waveforms - II

Four eccentric mergers

… maybe

Romero-Shaw, PL, Thrane 2022

eccentricity

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Many challenges; some in our control ...

Waveforms/data quality

GW200129

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Many challenges; some in our control ...

Waveforms/data quality

Hannam+2023

  • GW200129 is a strongly-precessing binary

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Many challenges; some in our control ...

Waveforms/data quality

Hannam+2023

  • GW200129 is a strongly-precessing binary

Payne+2023

  • No, it's not!
  • Data quality issue...

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Many challenges; some in our control, others not!

Low-frequency noise

cosmicexplorer.org

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Low-frequency noise

Many challenges; some in our control, others not!

cosmicexplorer.org

Cahillane & Mansell 2022

Buikema + 2020

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Low-frequency noise

Many challenges; some in our control, others not!

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Statistical detection before 2030 

… and �THE 

GOOD

We can overcome these issues

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Summary:

  • ~90 events, increasing quickly�
  • Statistical detection of memory takes ~1000 events�
  • Systematic problems to solve:
    • They are a pain for detecting memory
    • But they are interesting astrophysics questions 

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… and �THE 

GOOD

Question for this audience:

Suppose we detect memory in this way – what do we learn about the gravity?

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Abbott et al. (2020)

GW150914

600

400

200

0

0

90

180

distance [Mpc]

orientation (deg)

primary mass [M☉]

secondary mass [M☉]

30

40

50

25

35

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Abbott et al. (2020)

GW170817

GW150914

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Abbott et al. (2020)

GW170817

GW150914

GW190425

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Abbott et al. (2020)

GW170817

GW150914

GW190425

GW190521

  • Most massive system measured to date!
  • Eccentric orbit (Romero-Shaw, PL & Thrane 2020)
  • How did it form? Dynamical merger / second generation!?

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Abbott et al. (2020)

GW170817

GW150914

GW190425

GW190814

Most massive neutron star?

Lightest black hole?

GW190521

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Abbott et al. (2020)

GW170817

GW150914

GW190425

GW190814

GW190521

GW200105

GW200105

Image: Carl Knox