ilya mandel seminar nithep ukzn 20 jan 2014
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LIGO
GWastrophysicsof compact binaries
Ilya Mandel(University of Birmingham)
January 20, 2014UKZN, Durban
UKZN: Jan 20, 2014 2
UKZN: Jan 20, 2014
Gravitational Waves
Ripples in spacetime:
Caused by time-varying mass quadrupole moment; GW frequency is twice the orbital frequency for a circular, non-spinning binary
Huge amounts of energy released: GW energy output of SMBH binary greater than EM radiation from entire galaxy over a Hubble time
3
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Indirect observations of GWs PSR 1913+16 Discovered in 1974 GR precession of 4.2 deg/
yr (vs. 43 arcsec/century for Mercury, out of 5600)
5J0737-3039A: [Kramer et al., 2005]
UKZN: Jan 20, 2014
Opportunity and ChallengeGWs carry a lot of energy, but interact weakly: can pass through everything, including detectors!
Michelson-type interferometers
6
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Detection Challenges
7
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Detection Challenges
8
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LIGO Noise Spectrum
9
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A few initial LIGO/Virgo highlights GRB070201 overlapped
Andromeda (at 770 Mpc); binary coalescence in M31 excluded at >99% confidence [LSC+Hurley, 2008, ApJ 681 1419]
Best upper limit (Ω0 < 6.9 x 10-6) on stochastic background energy density at 100 Hz [LVC, 2009, Nature 460 990]
Beat spindown limit on emission from Crab (<0.02 E) and Vela (<0.45 E) pulsars, [LVC, 2008, ApJL 683 45; 2011, ApJ 737 93]
10
M31, GRB 070201
UKZN: Jan 20, 2014
Types of GW sources Continuous sources [sources with a slowly
evolving frequency]: e.g., non-axisymmetric neutron stars, slowly evolving binaries
Coalescence sources [known waveforms, matched filtering]: compact object binaries
Burst events [unmodeled waveforms]: e.g., asymmetric SN collapse, cosmic string cusps
Stochastic GW background [early universe]
??? [expect the unexpected]
11
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Predicting merger rates
12
Method Strength WeaknessDirect extrapolation from observed Galactic binaries
Most direct available probe; ~10 known (~5 merging) Galactic binary pulsars
Low statistics, poorly known selection effects, only relevant for BNS systems
UKZN: Jan 20, 2014
Predicting merger rates
13
Method Strength WeaknessDirect extrapolation from observed Galactic binaries
Most direct available probe; ~10 known (~5 merging) Galactic binary pulsars
Low statistics, poorly known selection effects, only relevant for BNS systems
Extrapolation from short GRB rates
Potentially direct probe of mergers involving NS out to large distances (z~2)
Uncertain provenance, ill-constrained beaming factors and selection effects
UKZN: Jan 20, 2014
Predicting merger rates
14
Method Strength WeaknessDirect extrapolation from observed Galactic binaries
Most direct available probe; ~10 known (~5 merging) Galactic binary pulsars
Low statistics, poorly known selection effects, only relevant for BNS systems
Extrapolation from short GRB rates
Potentially direct probe of mergers involving NS out to large distances (z~2)
Uncertain provenance, ill-constrained beaming factors and selection effects
Population synthesis of isolated binaries
UKZN: Jan 20, 2014
Population synthesis models No observed NS-BH or BH-BH binaries Predictions based on population-synthesis
models for isolated binary evolution with StarTrack [Belczynski et al., 2005, astro-ph/0511811] or similar codes
Many poorly constrained parameters: SN kicks, stellar winds, mass transfer efficiency, common envelope physics [O’Shaughnessy et al., 2005 ApJ 633 1076; 2008 ApJ 672 479]
Also: metallicity variations, SN mechanism/fallback, fate of Hertzsprung gap donor in common envelope... [Dominik et al., 2012 ApJ, 759, 52]
15
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Population synthesis predictions
16
[Dominik et al., 2012 ApJ, 759, 52]
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Predictions of component mass distributions
17[Dominik et al., 2012 ApJ, 759, 52]
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Predicting merger rates
18
Method Strength WeaknessDirect extrapolation from observed Galactic binaries
Most direct available probe; ~10 known (~5 merging) Galactic binary pulsars
Low statistics, poorly known selection effects, only relevant for BNS systems
Extrapolation from short GRB rates
Potentially direct probe of mergers involving NS out to large distances (z~2)
Uncertain provenance, ill-constrained beaming factors and selection effects
Population synthesis of isolated binaries
Applies to all binary types, creates models for future astrophysical inference
A number of poorly known input parameters (SNe kicks, winds, common envelope)
Source Rlow
Rhigh
NS-NS (MWEG�1 Myr�1) 1 1000NS-BH (MWEG�1 Myr�1) 0.05 100BH-BH (MWEG�1 Myr�1) 0.01 30
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Merger Rate Predictions
19
S6 / VSR2,3 Upper Limits
Predicted rates
[Abadie et al., 2011]
[Abadie et al., CQG 27:173001,2010]
UKZN: Jan 20, 2014
Predicting merger rates
20
Method Strength WeaknessDirect extrapolation from observed Galactic binaries
Most direct available probe; ~10 known (~5 merging) Galactic binary pulsars
Low statistics, poorly known selection effects, only relevant for BNS systems
Extrapolation from short GRB rates
Potentially direct probe of mergers involving NS out to large distances (z~2)
Uncertain provenance, ill-constrained beaming factors and selection effects
Population synthesis of isolated binaries
Applies to all binary types, creates models for future astrophysical inference
A number of poorly known input parameters (SNe kicks, winds, common envelope)
Forward evolution of observed X-ray binaries
Combination of observations and population synthesis
Uncertain selection effects, mass measurements, and modeling assumptions
UKZN: Jan 20, 2014
Predicting merger rates
21
Method Strength WeaknessDirect extrapolation from observed Galactic binaries
Most direct available probe; ~10 known (~5 merging) Galactic binary pulsars
Low statistics, poorly known selection effects, only relevant for BNS systems
Extrapolation from short GRB rates
Potentially direct probe of mergers involving NS out to large distances (z~2)
Uncertain provenance, ill-constrained beaming factors and selection effects
Population synthesis of isolated binaries
Applies to all binary types, creates models for future astrophysical inference
A number of poorly known input parameters (SNe kicks, winds, common envelope)
Forward evolution of observed X-ray binaries
Combination of observations and population synthesis
Uncertain selection effects, mass measurements, and modeling assumptions
Dynamical formation in dense environments
Independent scenario, less sensitive to binary evolution
Poorly known dynamics of globular and nuclear clusters
NG (L10) =43�
�Dhorizon
Mpc
⇥3
(2.26)�3(0.02)
N = R�NG
�(Dhorizon) � 8
UKZN: Jan 20, 2014
LIGO sensitivity
|h(f)| = 2/D � (5µ/96)1/2(M/⇥2)1/3f�7/6
(merger rate) = (merger rate per L10) * (NG in L10's)
� �
⇥
4� fISCO
0
|h(f)|2Sn(f)
df
1/2.26 -- sky and orientation averaging; 0.02 L10 per Mpc3
S4 S5 aLIGO
[plot from Kopparapu et al., 2008 ApJ 675 1459 ]
22
101
102
103
10−23
10−22
10−21
10−20
10−19
f, Hz
!S
n(f
),1/
!H
z
Initial LIGO
Initial Virgo
Advanced LIGO
Advanced Virgo
IFO Source Nlow
Nhigh
yr�1 yr�1
NS-NS 2⇥ 10�4 0.2Initial NS-BH 7⇥ 10�5 0.1
BH-BH 2⇥ 10�4 0.5NS-NS 0.4 400
Advanced NS-BH 0.2 300BH-BH 0.4 1000UKZN: Jan 20, 2014
Merger and Detection Rates
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[IM & O’Shaughnessy, 2010, CQG 27 114007;Abadie et al., CQG 27:173001, 2010, arXiv:1003.2480]
UKZN: Jan 20, 2014
Advanced LIGO overviewWhat is Advanced?
EOMLaser
Parameter Initial LIGO Advanced LIGO
Input Laser Power
10 W (10 kW arm)
180 W (>700 kW arm)
Mirror Mass 10 kg 40 kg
Interferometer Topology
Power-recycled
Fabry-Perot arm cavity Michelson
Dual-recycled Fabry-Perot arm cavity Michelson
(stable recycling cavities)
GW Readout Method
RF heterodyne DC homodyne
Optimal Strain Sensitivity
3 x 10-23 / rHz Tunable, better than 5 x 10-24 / rHz in broadband
Seismic Isolation Performance
flow ~ 50 Hz flow ~ 13 Hz
Mirror Suspensions
Single Pendulum
Quadruple pendulum slide courtesy
of Dave Reitze
UKZN: Jan 20, 2014
Advanced detector prospects
25[Aasi+ (LSC+Virgo), arXiv:1304.0670]
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The case of the buried signal
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Spectrograms
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Burst searches• Coherent WaveBurst: An algorithm which is used for unmodeled searches in a
wide parameter space that could detect all parts of the coalescence event
• Omega pipeline: Multi-resolution time-frequency search, equivalent to a template-based search for sinusoidal Gaussians in whitened data
Laura CadonatiG070801-00 28
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The case of the resurrected signal
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+
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Matched filteringFilter
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slide courtesy of Damir Buskulic
M � 50M�
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Waveform families Typical frequency scales
as 1/Mass For massive systems
( for LIGO), merger and ringdown contribute significantly to signal-to-noise ratio (SNR)
Spins add complications
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INSPIRAL:post-Newtonian
approximate waveforms
RINGDOWN:perturbative
solutionsMERGER:
need Numerical Relativity!
UKZN: Jan 20, 2014
Background estimation
tsignal?
Hanford 1Virgo
background coincidence32
Background is highly non-Gaussian
Can be estimated with time slides between detectors
Gaussian
Non-Gaussian tails
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False Alarm estimation
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Candidate GW100916 recovered with estimated False Alarm Rate < 1 in 7,000 years! [Abadie et al., Phys. Rev. D 85, 082002 (2012)]
UKZN: Jan 20, 2014
The Big Dog
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Astrophysics: the Inverse Problem Comparing predicted rates of binary mergers with model
predictions can allow us to constrain the input (astro)physics» Even non-trivial upper limits can do the trick:
37[IM & O’Shaughnessy, 2010, CQG 27 114007]
UKZN: Jan 20, 2014
Astrophysics: the Inverse Problem Comparing predicted rates of binary mergers with model
predictions can allow us to constrain the input (astro)physics
Can learn a lot more by comparing distributions of observed parameters (masses, spins) with model predictions
38
UKZN: Jan 20, 2014
Predictions of component mass distributions
39[Dominik et al., 2012 ApJ, 759, 52]
UKZN: Jan 20, 2014
Astrophysics: the Inverse Problem Comparing predicted rates of binary mergers with model
predictions can allow us to constrain the input (astro)physics
Can learn a lot more by comparing distributions of observed parameters (masses, spins) with model predictions» Requires accurate parameter estimation on individual sources
40
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Parameter estimation: challenges
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Explore a large physical parameter space: 9 to 15 dimensions
Analyze data streams coherently Make use of a priori information Infer posterior distribution on signal parameters Could be multi-modal:
UKZN: Jan 20, 2014
Solution: Bayesian inference & stochastic sampling
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[van der Sluys et al., 2008, 2008, 2009; Veitch & Vecchio, 2008, 2008; Raymond et al., 2009,2010; Farr and IM, 2011; Veitch et al., 2012...]
UKZN: Jan 20, 2014 43
UKZN: Jan 20, 2014
Accurate Parameter Estimation
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van der Sluys, IM, Raymond, et al., 2009, CQG 26, 204010
UKZN: Jan 20, 2014
Astrophysics: the Inverse Problem Comparing predicted rates of binary mergers with model
predictions can allow us to constrain the input (astro)physics
Can learn a lot more by comparing distributions of observed parameters (masses, spins) with model predictions» Requires accurate parameter estimation on individual sources» Requires combining information from multiple events to construct a
statement about population distribution (accounting for selection bias, etc.)» Requires a library of catalogs of simulations based on different assumed
astrophysical parameters» Requires a pipeline for comparing observations and catalogs» We need to be able to test population synthesis models themselves: need
to over-determine the parameters... how many detections will this require? what will be the correlations/degeneracies in the astrophysical parameter space?
45
UKZN: Jan 20, 2014
Astrophysics: the Inverse Problem Comparing predicted rates of binary mergers with model
predictions can allow us to constrain the input (astro)physics
Can learn a lot more by comparing distributions of observed parameters (masses, spins) with model predictions
(Almost) Model-independent inference
46
» Evidence for a mass gap? [Dominik, IM, Belczynski, in prep.]
UKZN: Jan 20, 2014
Astrophysics: the Inverse Problem Comparing predicted rates of binary mergers with model
predictions can allow us to constrain the input (astro)physics
Can learn a lot more by comparing distributions of observed parameters (masses, spins) with model predictions
More model-independent inference
47
» Search for subpopulations (e.g., distinguish isolated and dynamically formed BH-BH binaries based on spin-orbit alignment)
» Directly measure time delays by observing dependence of merger rate on redshift [IM+, in prep.]
UKZN: Jan 20, 2014
Astrophysics: the Inverse Problem Comparing predicted rates of binary mergers with model
predictions can allow us to constrain the input (astro)physics
Can learn a lot more by comparing distributions of observed parameters (masses, spins) with model predictions
More model-independent inference
48
» Search for subpopulations (e.g., distinguish isolated and dynamically formed BH-BH binaries based on spin-orbit alignment)
» Measure binary kick velocities from GWs without EM counterparts [L. Kelley et al., 2010, ApJL 725 L91]
UKZN: Jan 20, 2014
Multimessenger astronomy “Holy grail of GW astronomy”
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Targeted archival search
GWs from binary merger
EM transient
Rapid(?) followup
GW candidate
EM counterpart
survey
deep pointing
UKZN: Jan 20, 2014
Cosmology with Advanced Detectors GWs as standard candles [Schutz, Nature, 1986]
Mass-redshift degeneracy can be broken by:» Direct EM associations [e.g. Nissanke et al., 2010]» Statistical EM associations [Schutz, 1986 and others]» Tidal effects [Messenger & Read, 2011] » Knowledge of mass distribution [Taylor, Gair, IM, 2011]
Could independently measure Hubble constant:
50
UKZN: Jan 20, 2014
Testing GR with extreme-mass-ratio inspirals
LIGO sensitive @ a few hundred Hz» NS-NS, NS-BH, BH-BH binaries » and intermediate-mass-ratio
inspirals of NSs or BHs into IMBHs– could observe up to tens per year
[IM+, 2008, ApJ 681 1431]
LISA sensitive @ a few mHz» massive black-hole binaries» galactic white dwarf (and compact
object) binaries» extreme-mass-ratio inspirals of
WDs/NSs/BHs into SMBHs– could observe tens to hundreds to
z~1 [e.g., Amaro-Seoane et al., 2007, CQG 24 R113]
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Extreme Mass Ratio Inspirals
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Exploring the spacetime...
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... taking lots of pictures
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Testing the “no-hair” theorem
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Testing the no-hair theorem
UKZN: Jan 20, 2014 57
Testing the no-hair theorem?
Stationary, vacuum, asymptotically flat spacetimes in which the singularity is fully enclosed by a horizon with no closed timelike curves outside the horizon are described by the Kerr metric
UKZN: Jan 20, 2014 58
Do black holes have hair?
Ryan’s theorem [1995]: GWs from nearly circular, nearly equatorial orbits in stationary, axisymmetric spacetimes encode all of the spacetime multipole moments... in principle
Manko-Novikov spacetime, an exact solution of Einstein’s equations:
Search for observable imprints of a “bumpy” spacetime, such as deviations from the full set of isolating integrals (energy, angular momentum, Carter constant) in Kerr [Gair, Li, IM, 2009, PRD 77:024035]
UKZN: Jan 20, 2014
The emergence of chaos
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Solve the geodesic equation and study Poincare maps:
- Plot dρ/dt vs. ρ for z=z0 crossings- Phase space plots should be closed curves for all z0 iff there is a third isolating integral [Carter constant]
Newtonian+hexadecapole:
M2=10 M0; M4=400 M0
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Order and Chaos, side by side
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integral.
0 2 4 6 8 10 12 14−5
−4
−3
−2
−1
0
1
2
3
4
5
ρ/Μ
z/M
FIG. 4: E!ective potential for geodesic motion around a bumpy black hole with ! = 0.9, q = 0.95,
E = 0.95, and Lz = 3M . The thick dotted curves indicate zeros of the e!ective potential. The
trajectory of a typical geodesic in the outer region is shown by a thin curve. The regular pattern of
self-intersections of the geodesic projection onto the "!z plane indicates (nearly) regular dynamics.
If |q| is increased from the value shown in Figure 4, the two regions of bound motioneventually merge. When this first occurs, the “neck” joining the regions is extremely narrow.Geodesics exist which can pass through the neck, but this requires extreme fine tuning. As|q| is further increased, the neck gradually widens and eventually disappears. At that stage,the single allowed region for bound orbits has a similar shape to the outer region of Figure 4.
These general properties of the e!ective potential seem to be common to all spacetimeswith q > 0 and ! "= 0. More relevant for the EMRI problem is to fix q and ! and to varyE and Lz . For E = 1 and su"ciently large Lz, there are two regions of allowed motionbounded away from the origin, in addition to the plunging zone connected to the singularityat " = 0, |z| # 1. The outermost of the allowed regions stretches to infinity and containsparabolic orbits. The inner region of bounded motion is the analogue of the inner boundregion described above and lies very close to the central object. If the angular momentumis decreased, while keeping E = 1, the two non-plunging regions get closer together andeventually merge to leave one allowed region that stretches to infinity. For fixed E < 1the behavior is qualitatively the same, except that for Lz $ M there is no outer region(there is a maximum allowed angular momentum for bound orbits of a given energy, as inthe Kerr spacetime). As Lz is decreased, the outer region for bound motion appears andthen eventually merges with the inner region. Decreasing Lz further eventually causes the
11
f
UKZN: Jan 20, 2014
Other signs of non-Kerr spacetimes Location and character of ISCO
Periapsis and orbital-plane precession
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1
2
3
4
5
6
7
8
-4 -2 0 2 4
ρIS
CO
/M
q
Radially unstable - first branchRadially unstable - second branch
Vertically unstable
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0.22
-4 -2 0 2 4
(MΩφ) I
SC
O
q
Radially unstable - first branchRadially unstable - second branch
Vertically unstable
FIG. 11: Properties of the equatorial ISCO in spacetimes with ! = 0, as a function of q. We show
the " coordinate of the ISCO (left panel) and the dimensionless frequency of the orbit at the ISCO
(right panel). As described in the text, the ISCO radius has three branches, depending on whether
it is determined by one of the two branches of radial instability or the branch of vertical instability.
These branches are indicated separately in the diagram. For values of q where all three branches
are present, the dashed line denotes the “OSCO” and the dotted line denotes "ISCO as discussed
in the text. Allowed orbits lie above the curve in the left panel, and below the curve in the right
panel.
comparatively small deviations from Kerr.
V. PERIAPSIS AND ORBITAL-PLANE PRECESSIONS
In Section III we saw that astrophysically relevant orbits in the Manko-Novikov space-time are multi-periodic to high precision. In such cases, there is no smoking-gun signaturethat indicates the presence of “bumpiness” in the spacetime. Instead, the imprint of thespacetime bumpiness will be observationally apparent in the location of the last stable orbit,as discussed in the previous section, and in the following ways: (1) in the three fundamen-tal frequencies of the gravitational waves generated while the inspiraling object is on aninstantaneous geodesic orbit; (2) in the harmonic structure of the gravitational-wave emis-sion, i.e., the relative amplitudes and phases of the various harmonics of the fundamentalfrequencies; and (3) in the evolution of these frequencies and amplitudes with time as theobject inspirals. A full analysis of the accuracies that could be achieved in observationswould involve computing gravitational waveforms in the bumpy spacetimes, performing aFisher-Matrix analysis to account for parameter correlations, and comparing to a similaranalysis for Kerr. That is beyond the scope of this paper. However, we can examine thefirst of these observational consequences by comparing the fundamental frequencies betweenthe bumpy and Kerr spacetimes.
The complication in such an analysis is to identify orbits between di!erent spacetimes.
24
-4
-2
0
2
4
-0.06 -0.04 -0.02 0 0.02 0.04 0.06
Δ pρ
MΩφ
q = -0.5q = -1
q = -5q = 0.5
q = 1q = 5
FIG. 17: Di!erence between periapsis precessions in a bumpy spacetime with ! = 0 and the
Schwarzschild spacetime, "p!(#", q) = p!(#", q) ! p!(#", q = 0).
the precession (see Eq. (B15) in the Appendix) then gives
p! =
!
3 (M!0)2
3 ! 4! (M!0) +3
2
"
9 + !2 + q#
(M!0)4
3 + · · ·$
+%
2 (M!0)2
3 ! 4! (M!0) + 2"
9 + !2 + q#
(M!0)4
3 + · · ·& !" ! !0
!0
+
!
!1
3(M!0)
2
3 +1
3
"
9 + !2 + q#
(M!0)4
3 + · · ·$ !
!" ! !0
!0
$2
+ · · ·
= b0 + b1!" ! !0
!0+ b2
!
!" ! !0
!0
$2
+ · · · (24)
In this kind of expansion the multipole moments again contribute at all orders. However,provided the initial frequency !0 " 1, the dominant piece of the constant term, b0, is(M!0)
2
3 , so this term can be used to estimate M . Similarly, the dominant piece of 2b0 ! 3b1
is 4! (M!0), so this can be used to estimate !, and that estimate of ! can be used to improve
the estimate of M from b0. The dominant piece of b0 ! b1 + 3b2 is (9 + !2 + q) /2 (M!0)4
3 ,so this can be used to estimate the excess quadrupole moment q and so on. In the sameway, if an eccentric inspiral is observed in a regime where the initial frequency is small (andhence the frequency at capture was also small), we can use the same type of expansion anduse combinations of the coe"cients to successively extract each multipole moment and theinitial eccentricity. To do this requires an expansion of e2 ! e2
0 as a function of !"/!0 ! 1.The necessary derivatives de2/d(M!") are known in the weak-field, and to lowest orderin the multipoles (see, for example, reference [22]). However, this calculation is somewhatinvolved, so we leave it for a future paper.
33
-1
-0.5
0
0.5
1
1.5
2
-0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25
Δ p
z
MΩφ
q = -0.5q = -1
q = -5q = 0.5
q = 1q = 5
FIG. 19: Di!erence between orbital-plane precessions in a bumpy spacetime with ! = 0.9 and the
Kerr spacetime with ! = 0.9, "pz(#!, q) = pz(#!, q) ! pz(#!, q = 0).
from large distances. Most astrophysically relevant orbits are regular and appear to possessan approximate fourth integral of the motion, and the orbits are tri-periodic to high accu-racy. The deviations of the central body from Kerr then manifest themselves only in thechanges in the three fundamental frequencies of the motion and the relative amplitude ofthe di!erent harmonics of these frequencies present in the gravitational waves. For nearlycircular, nearly equatorial orbits, the dependence of the precession frequencies on the orbitalfrequency is well fit by a combination of a weak field expansion that encodes the multipolemoments at di!erent orders, plus a term that diverges as the innermost stable circular orbitis approached. The frequency of the ISCO and its nature (whether it is defined by a radialor vertical instability) is another observable signature of a non-Kerr central object.
To derive these results, we have focussed on a particular family of spacetimes due toManko and Novikov [8]. However, we expect the generic features of the results in the weakfield and as the ISCO is approached to be true for a wide range of spacetimes. Chaos has beenfound for geodesic motion in several di!erent metrics by various authors [9, 10, 11, 12, 13].In all cases, however, the onset of chaos was qualitatively similar to what we found here— it occurred only very close to the central object, and for a very limited range of orbitalparameters. The conclusion that gravitational waves from ergodic EMRIs are unlikely to beobserved is thus probably quite robust.
Precessions for spacetimes that deviate from the Kerr metric have also been consideredby several authors [2, 6, 7]. Our results agree with this previous work in the weak-field as itshould. However, the results in the present paper are the first that are valid in the strong-field since previous work was either based on a weak-field expansion [2] or a perturbativespacetime [6, 7]. The main feature of the precessions in the strong-field — the divergence of
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10−6 10−5 10−4 10−3 10−2 10−110−1
100
101
102
103
104
105
106
d
Accu
mul
ated
cyc
le d
iffer
ence
3.5 PN vs 3 PN, M=1e4 Msun3.5 PN vs 3 PN, M=1e5 Msun3.5 PN vs 3 PN, M=1e6 Msun3.5 PN vs EMRI, M=1e4 Msun3.5 PN vs EMRI, M=1e5 Msun3.5 PN vs EMRI, M=1e6 Msun
UKZN: Jan 20, 2014
Measuring the mass quadrupoleCan measure mass quadrupole moment to around 20% of Kerr value with Advanced LIGO [Brown et al., 2007, PRL 99, 201102]
62
Waveforms are a problem: both post-Newtonian and self-force waveforms currently fail in the intermediate regime [IM and Gair, 2009, PRD 72 084025]
UKZN: Jan 20, 2014
IMRI: null-hypothesis test of Kerrness
63
[Rodriguez, IM, Gair, PRD 85, 062002]
UKZN: Jan 20, 2014
Summary Advanced LIGO is likely to observe GWs from NS-NS,
NS-BH, BH-BH coalescences; tens or more coalescences may be observed according to some models, including signatures of dynamical formation
GW detections and upper limits for compact-object coalescences will allow us to constrain astrophysical parameters through comparisons with model predictions
Extreme- or intermediate- mass-ratio inspirals can serve as precise tests of General Relativity
There’s lots of work to be done in order to make true GWastrophysics a reality!
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