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Gravitational wave astronomy: a facilities overview Barry C. Barish Caltech AAS San Diego 13-Jan-05. LISA. Towards Detection of Gravitational Waves. From LISA Concept Demonstrations Mission From Bars Bars with Increased Bandwidth Spheres

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Gravitational wave astronomy a facilities overview barry c barish caltech aas san diego 13 jan 05

Gravitational wave astronomy: a facilities overviewBarry C. BarishCaltechAASSan Diego13-Jan-05


Towards detection of gravitational waves
Towards Detection of Gravitational Waves

  • From LISA Concept Demonstrations Mission

  • From Bars Bars with Increased Bandwidth Spheres

  • From Interferometers Advanced Interferometers Next Generation (QND) Detectors

  • From 6 Mpc (NN inspiral) 200 Mpc and then beyond

  • From Upper Limits Searches Detections

  • From Generic Searches Searches with Specified Waveforms

  • From Single Detectors Global Networks

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Gravitational waves in space
Gravitational Waves in Space


Three spacecraft, each with a Y-shaped payload, form an equilateral triangle with sides 5 million km in length.

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The three LISA spacecraft will be placed in orbits that form a triangular formation with center 20o behind the Earth

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Each spacecraft will be in an Earth-like orbit around the Sun and the triangle appears to rotate through the year.

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'Y'-shaped payload has two identical optical assemblies with transmit/receive telescopes and optical benches carrying the inertial sensor and the interferometry optics. The inertial sensor consists of a free-falling proof mass inside a reference housing, which is fixed to the spacecraft.

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The diagram shows the sensitivity bands for LISA and LIGO

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Black Hole

Binary Inspirals

A coalescence of two 105, 106 and107 solar mass black holes

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Resonant Bar Detectors


The Netherlands

Auriga, Italy

Allegro USA




Nautilus, italy






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The resonant transducer
The resonant transducer

The displacement of the secondary oscillator

modulates a dc electric or magnetic field or

the frequency of a s.c. cavity



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Sensitivity of resonant detectors
Sensitivity of Resonant Detectors

  • Noise in the detector

  • Extrinsic: Seismic noise  mechanical filter

  • Intrinsic: Thermal noise  cool detector

  • amplifier noise  SQUID amplifier



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LHe4 vessel

Al2081 holder

Electronics wiring support

Main Attenuator

Thermal Shield

Sensitive bar

Compression Spring



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2nd run: preliminary results







_Experimental results

_ Expected sensitivity

Spurious lines (x) are related to environmental noise but do not affect significantly the burst sensitivity e.g., for a 1 ms sin-gaussian pulse:

hmin≈ 3 x10-19 in both situation

Best result obtained when spurious lines fade out

Bandwidth: h < 5x10-21 Hz-1/2 within ~100 Hz band (noise floor)

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Network of resonant bars
Network of Resonant Bars






IGEC Network

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International gravitational event collaboration igec
International Gravitational Event Collaboration (IGEC)


  • The search for burst waves at resonant frequency ~ 900 Hz.

  • The detectors nearly parallel to maximize coincident sensitivity.

  • Candidate events at SNR > 3-5 (~background events 100/day)

  • Data exchanged: peak amplitude, time of event and uncertainties.

  • Threshold equivalent to ~0.1 M⊙ converted into a gravitational wave millisecond burst at a distance of 10 kpc.

  • The accidental coincidence rate over 1 sec interval (e.g. bandwidth of 1 Hz) was ~ few/week two-fold and ~few/century three-fold.

  • Time resolution not sufficient to resolve incident wave direction, no directional search has been applied.

  • No evidence for grav wave bursts was found.

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IGEC coincidence search

Upper Limit on the Rateof gravitational waves bursts from the GALACTIC CENTERrandom arrival times and amplitude  search threshold h

Final results


[y –1]

The Area above the blue curve

is excluded with a coverage > 90%

search threshold h

h~ 2 10-18

DE ~ 0.02 M⊙ converted @ 10 kpc

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[P. Astone, et al. Phys. Rev. D68 (2003) 022001]


During 2001 EXPLORER and NAUTILUS were the only two operating resonant detectors, with the best ever reached sensitivity.

An algorithm based on energy compatibility of the event was applied to reduce the “background”

Excess ???

Direction of Galactic Disc

Number of events

Sidereal hours

ROG Coll.: CQG 19, 5449 (2002)

L.S.Finn: CQG 20, L37 (2003)

P.Astone, G.D’Agostini, S.D’Antonio: CQG Proc. Of GWDAW 2002, gr-qc/0304096

E. Coccia ROG Coll.:CQG Proc. Of GWDAW 2002

ROG Coll.: gr-qc/0304004

New data is needed with more antennas in coincidence !

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Resonant spheres
Resonant Spheres

The future??


  • Much larger cross-section than a bar of the same resonant frequency (up to 70 x)

  • Omni-directional: Allows for the determination of direction and polarization

  • Require 6 transducers

  • Hollow spheres could allow a choice of cross-sections and frequencies

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LIGO Louisiana 4000m

TAMA Japan 300m

Virgo Italy 3000m

GEO Germany 600m

AIGO Australia future

LIGO Washington 2000m & 4000m

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Network of interferometers
Network of Interferometers






decompose the polarization of gravitational waves

detection confidence

locate the sources

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Astrophysical sources
Astrophysical Sources

  • Compact binary inspiral: “chirps”

    • NS-NS waveforms are well described

    • BH-BH need better waveforms

    • search technique: matched templates

  • Supernovae / GRBs: “bursts”

    • burst signals in coincidence with signals in electromagnetic radiation

    • prompt alarm (~ one hour) with neutrino detectors

  • Pulsars in our galaxy: “periodic”

    • search for observed neutron stars (frequency, doppler shift)

    • all sky search (computing challenge)

    • r-modes

  • Cosmological Signals “stochastic background”

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Ligo science has begun
LIGO Science Has Begun

Three Science Runs(S1--S3) interspersed with commissioning

S1 run: Primarily methods papers - 17 days (Aug - Sep 2002)Four S1 astrophysical searches published (Phys. Rev. D 69, 2004):

  • Inspiraling neutron stars122001

  • Bursts102001

  • Known pulsar (J1939+2134) with GEO082004

  • Stochastic background122004

    S2 run:S2 analyses are mostly complete - 59 days (Feb - April 2003)

  • Results presented at APS 2004 Spring Meeting

  • GR-17 (Dublin)

  • Gravitational Wave Data Analysis Workshop (GWDAW) in Annecy, France (December 2004)

    S3 run: Analysis is in full swing - 70 days (Oct 2003 – Jan 2004)

  • Analysis is in full swing; preliminary results becoming available for GWDAW meeting in Annecy, France

A number of drafts of S2, S3 papers under review by collaboration

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Detection of periodic sources
Detection of Periodic Sources

  • Pulsars in our galaxy: “periodic”

    • search for observed neutron stars

    • all sky search (computing challenge)

    • r-modes

  • Frequency modulation of signal due to Earth’s motion relative to the Solar System Barycenter, intrinsic frequency changes.

  • Amplitude modulation due to the detector’s antenna pattern.

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PSR J1939+2134

1283.86 Hz

Directed searches


at present sensitivities

Crab Pulsar

Limits of detectability for rotating NS with equatorial ellipticity e = dI/Izz: 10-3 , 10-4 , 10-5 @ 8.5 kpc.

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Summary of s2 results limits on strain

Crab pulsar

Marginalized Bayesian PDF for h







J1910 – 5959D:

h0 = 1.7 x 10-24



Summary of S2 resultslimits on strain

Red dots: pulsars are in globular clusters - cluster dynamics hide intrinsic spin-down properties

Blue dots: field pulsars for which spin-downs are known

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Summary s2 results ellipticity limits

LIGO upper-limits from hmax




EM spin-down upper-limits

Summary S2 results - ellipticity limits

  • Best upper-limits:

  • J1910 – 5959D: h0 < 1.7 x 10-24

  • J2124 – 3358:  < 4.5 x 10-6

  • How far are S2 results from spin-down limit? Crab: ~ 30X

Red dots: pulsars are in globular clusters - cluster dynamics hide intrinsic spin-down properties

Blue dots: field pulsars for which spin-downs are known

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Advanced ligo
Advanced LIGO

Multiple Suspensions

Active Seismic

Sapphire Optics

Higher Power Laser

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Advanced ligo1
Advanced LIGO

2007 +

  • Enhanced Systems

  • laser

  • suspension

  • seismic isolation

  • test mass


Improvement ~ 104


narrow band

optical configuration

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  • Sensitivity toward gravitational wave detection is improving on many fronts and this will continue into the future

  • Improved upper limits are being set for all major sources -- binary inspirals, periodic sources, burst sources and stochastic background

  • Transition is being made from data analysis oriented toward upper limit setting to analysis aimed at detection

  • Data exchange and joint data analysis between detector groups is improving our ability to make detections

  • Need specific waveforms to improve search sensitivities!

  • Hopefully, detections will be made soon !!

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