Gravitational wave astronomy: a facilities overview

Barry C. BarishCaltech

AASSan Diego13-Jan-05

LISA

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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

LISA

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

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LISA

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

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LISA

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.

LISA

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LISA

The diagram shows the sensitivity bands for LISA and LIGO

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LISA

A coalescence of two 105, 106 and 107 solar mass black holes

MassiveBlack Hole

Binary Inspirals

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ExplorerSwitzerland

Allegro USA

SchenbergBrazil

MiniGrailThe Netherlands

NiobeAustralia

Nautilus, italy

Auriga, ItalyResonant Bar Detectors

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The resonant transducer

xM xm

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

Noise in the detector

Extrinsic: Seismic noise ⇒ mechanical filter

Intrinsic: Thermal noise ⇒ cool detector

amplifier noise ⇒ SQUID amplifier

transducer

amplifier

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AURIGA

Transducer

Electronics wiring support

LHe4 vesselAl2081 holder

Main Attenuator

Compression Spring

Thermal ShieldSensitive bar

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AURIGA

Bandwidth: h < 5x10-21 Hz-1/2

within ~100 Hz band (noise floor)

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

_ Experimental results_ Expected sensitivity

**

*

**

*

2nd run: preliminary results

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Network of Resonant Bars

Allegro Explorer Auriga

Nautilus

NiobeIGEC Network

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International Gravitational Event Collaboration (IGEC)

ALLEGRO,AURIGA,EXPLORER, NAUTILUS, and NIOBE 1997-2000.

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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rate[y –1]

search threshold h

1.E+00

1.E+01

1.E+02

1.E+03

1E-18 1E-17 1E-16

IGEC

h ~ 2 10-18 ΔE ~ 0.02 M⊙ converted @ 10 kpc

The Area above the blue curveis excluded with a coverage > 90%

Upper Limit on the Rate of gravitational waves bursts from the GALACTIC CENTER

random arrival times and amplitude ≥ search threshold h

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

IGEC coincidence search

Final results

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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”

EXPLORER-NAUTILUS 2001

Sidereal hours

Num

ber o

f eve

nts

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/0304096E. Coccia ROG Coll.:CQG Proc. Of GWDAW 2002ROG Coll.: gr-qc/0304004

New data is needed with more antennas in coincidence !

Excess ???Direction of Galactic Disc

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Resonant Spheres

• 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

The future??TIGA

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InterferometerDetectors

LIGO Louisiana 4000mTAMA Japan

300m

Virgo Italy 3000m

GEO Germany 600mAIGO Australia

future

LIGO Washington 2000m & 4000m

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Network of Interferometers

LIGO

detection confidence

GEO VirgoTAMA

AIGOlocate the sources

decompose the polarization of gravitational waves

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Astrophysical SourcesCompact 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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Evolution of LIGO Sensitivity

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LIGO Science Has Begun

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

Inspiraling neutron stars 122001Bursts 102001Known pulsar (J1939+2134) with GEO 082004Stochastic background 122004

S2 run: S2 analyses are mostly complete - 59 days (Feb - April 2003)Results presented at APS 2004 Spring MeetingGR-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

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

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

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Detection of Periodic SourcesPulsars 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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Directed searches

( ) OBSGWh0 /TfS4.11h =

NO DETECTION EXPECTED

at present sensitivities

PSR J1939+21341283.86 Hz

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

Crab Pulsar

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Summary of S2 resultslimits on strain

S1

J1939+2134

S2J1910 – 5959D: h0 = 1.7 x 10-24

Crab pulsar

Red dots: pulsars are in globular clusters - cluster dynamics hide intrinsic spin-down propertiesBlue dots: field pulsars for which spin-downs are known

h95

1

PDF

0strain

Marginalized Bayesian PDF for

h

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EM spin-down upper-limits

LIGO upper-limits from hmax

J1939+2134S1

S2

Summary S2 results - ellipticity limits

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

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

Best upper-limits:

• J1910 – 5959D: h0 < 1.7 x 10-24

• J2124 – 3358: ε < 4.5 x 10-6

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

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Advanced LIGO

Active Seismic

Multiple Suspensions

Sapphire Optics

Higher Power Laser

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Advanced LIGO

Enhanced Systems• laser• suspension• seismic isolation• test mass

RateImprovement

~ 104

+narrow band

optical configuration

2007 +

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ConclusionsSensitivity 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 !!