gravitational wave astronomy: a facilities overviewbcbact/talks05/aas 01-05... · 2005. 7. 23. ·...
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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
**
*
**
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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
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 !!
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