Transcript AAS 01-05

Gravitational wave astronomy:
a facilities overview
LISA
Barry C. Barish
Caltech
AAS
San Diego
13-Jan-05
Towards Detection of
Gravitational Waves
 From LISA Concept
 From Bars
Demonstrations
Mission
Bars with Increased Bandwidth
Spheres
 From Interferometers
Advanced Interferometers
Generation (QND) Detectors
 From 6 Mpc (NN inspiral)
 From Upper Limits
 From Generic Searches
 From Single Detectors
13-Jan-05
Next
200 Mpc and then beyond
Searches
Detections
Searches with Specified Waveforms
Global Networks
AAS - Barish
2
Gravitational Waves in Space
LISA
Three spacecraft, each with a Y-shaped payload, form
an equilateral triangle with sides 5 million km in length.
13-Jan-05
AAS - Barish
3
LISA
The three LISA spacecraft will be placed in orbits that form
a triangular formation with center 20o behind the Earth
13-Jan-05
AAS - Barish
4
LISA
Each spacecraft will be in an Earth-like orbit around the
Sun and the triangle appears to rotate through the year.
13-Jan-05
AAS - Barish
5
LISA
'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.
13-Jan-05
AAS - Barish
6
LISA
The diagram shows the sensitivity bands for LISA and LIGO
13-Jan-05
AAS - Barish
7
LISA
Massive
Black Hole
Binary Inspirals
A coalescence of two 105, 106 and 107 solar mass black holes
13-Jan-05
AAS - Barish
8
Resonant Bar
Detectors
MiniGrail
The Netherlands
Auriga, Italy
Allegro USA
Schenberg
Brazil
Nautilus, italy
Explorer
Switzerland
13-Jan-05
AAS - Barish
Niobe
Australia
9
The resonant transducer
The displacement of the
secondary oscillator
modulates a dc electric
or magnetic field or
the frequency of a s.c.
cavity
xM
13-Jan-05
AAS - Barish
xm
10
Sensitivity of Resonant Detectors
Noise in the detector
Extrinsic: Seismic noise  mechanical filter
Intrinsic: Thermal noise  cool detector
amplifier noise  SQUID amplifier
amplifier
transducer
13-Jan-05
AAS - Barish
11
AURIGA
LHe4 vessel
Al2081 holder
Electronics
wiring support
Main Attenuator
Sensitive bar
Thermal
Shield
Compression Spring
13-Jan-05
AAS - Barish
Transducer
12
AURIGA
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)
13-Jan-05
AAS - Barish
13
Network of Resonant
Bars
Allegro
Explorer
Auriga
Nautilus
IGEC Network
13-Jan-05
AAS - Barish
Niobe
14
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.
13-Jan-05
AAS - Barish
15
IGEC coincidence search
Upper Limit on the Rate of gravitational waves bursts
from the GALACTIC CENTER
random arrival times and amplitude  search threshold h
Final results
1.E+03
IGEC
rate
[y –1]
1.E+02
The Area above the blue curve
is excluded with a coverage > 90%
1.E+01
1.E+00
1E-18
1E-17
1E-16
search threshold h
h ~ 2 10-18
13-Jan-05
DE ~ 0.02 M⊙ converted @ 10 kpc
AAS - Barish
[P. Astone, et al. Phys.
Rev. D68 (2003) 022001]
16
EXPLORER-NAUTILUS 2001
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 ???
Number of events
Direction of Galactic Disc
Sidereal hours
New data is needed with more
antennas in coincidence !
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
13-Jan-05
AAS - Barish
17
Resonant Spheres
The future??
TIGA
• 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
13-Jan-05
AAS - Barish
18
TAMA Japan
300m
Interferometer
Detectors
LIGO Louisiana
4000m
Virgo Italy
3000m
GEO Germany
600m
AIGO Australia
future
LIGO Washington
2000m & 4000m
13-Jan-05
AAS - Barish
19
Network of Interferometers
LIGO
GEO
decompose the polarization of
detection
locate the
confidence
sources
gravitational
waves
13-Jan-05
AAS - Barish
Virgo
TAMA
AIGO
20
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”
13-Jan-05
AAS - Barish
21
Evolution of LIGO Sensitivity
13-Jan-05
AAS - Barish
22
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 stars 122001
 Bursts 102001
 Known pulsar (J1939+2134) with GEO 082004
 Stochastic background 122004
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
13-Jan-05
AAS - Barish
23
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.
13-Jan-05
AAS - Barish
24
Directed searches
NO DETECTION
EXPECTED
at present
sensitivities
Crab Pulsar
h 0  11.4 Sh f GW /TOBS
Limits of detectability for
rotating NS with equatorial
ellipticity e = dI/Izz: 10-3 , 10-4 ,
10-5 @ 8.5 kpc.
PSR
J1939+2134
13-Jan-05
AAS - Barish
1283.86 Hz
25
Summary of S2 results
limits on strain
Crab pulsar
1
S1
J1939+2134
J1910 – 5959D:
PDF
h95
S2
0
h0 = 1.7 x 10-24
13-Jan-05
Marginalized
Bayesian PDF for
h
strain
Red dots: pulsars are in
globular clusters - cluster
dynamics hide intrinsic spindown properties
Blue dots: field pulsars for
which spin-downs are
known
AAS - Barish
26
Summary S2 results - ellipticity limits
Best upper-limits:
• J1910 – 5959D: h0 < 1.7 x 10-24
• J2124 – 3358: e < 4.5 x 10-6
How far are S2 results from
spin-down limit? Crab: ~ 30X
LIGO upper-limits from hmax
J1939+2134
S1
S2
EM spin-down upper-limits
13-Jan-05
AAS - Barish
Red dots: pulsars are in globular
clusters - cluster dynamics hide
intrinsic spin-down properties
Blue dots: field pulsars for which
spin-downs are known
27
Advanced LIGO
Multiple Suspensions
Active Seismic
Sapphire Optics
Higher Power Laser
13-Jan-05
AAS - Barish
28
Advanced LIGO
2007 +
Enhanced Systems
• laser
• suspension
• seismic isolation
• test mass
Rate
Improvement
~ 104
+
narrow band
optical configuration
13-Jan-05
AAS - Barish
29
Conclusions
 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 !!
13-Jan-05
AAS - Barish
30