Gravitational Wave Detection of Astrophysical Sources Barry C. Barish Caltech Neutrino Telescope Venice 24-Feb-05

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Gravitational Wave Detection of Astrophysical
Sources Barry C. BarishCaltechNeutrino
Telescope Venice24-Feb-05
Crab Pulsar
LIGO-xxx
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Einsteins Theory of Gravitation

• a necessary consequence of Special Relativity
  with its finite speed for information transfer
• gravitational waves come from the acceleration
  of masses and propagate away from their sources
  as a space-time warpage at the speed of light

gravitational radiation binary inspiral of
compact objects
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Einsteins Theory of Gravitation gravitational
waves

• Using Minkowski metric, the information about
  space-time curvature is contained in the metric
  as an added term, hmn. In the weak field limit,
  the equation can be described with linear
  equations. If the choice of gauge is the
  transverse traceless gauge the formulation
  becomes a familiar wave equation

• The strain hmn takes the form of a plane wave
  propagating at the speed of light (c).

• Since gravity is spin 2, the waves have two
  components, but rotated by 450 instead of 900
  from each other.

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Detectionof Gravitational Waves
Gravitational Wave Astrophysical Source
Terrestrial detectors Virgo, LIGO, TAMA, GEO AIGO
Detectors in space LISA
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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 diagram shows the sensitivity bands for LISA
and LIGO
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Detecting a passing wave .
Free masses
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Detecting a passing wave .
Interferometer
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Interferometer Concept

• Laser used to measure relative lengths of two
  orthogonal arms

• Arms in LIGO are 4km
• Measure difference in length to one part in 1021
  or 10-18 meters

causing the interference pattern to change at
the photodiode
Suspended Masses
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Simultaneous Detection
Hanford Observatory
MIT
Caltech
Livingston Observatory
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LIGO Livingston Observatory
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LIGO Hanford Observatory
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LIGO Goals and Priorities

• Interferometer performance
• Integrate commissioning and data taking
• Obtain one year of integrated data at h 10-21
  by 2008
• Physics results from LIGO I
• Initial upper limit results by early 2003
• First search to begin in 2005
• Reach LIGO I goals by 2008
• Advanced LIGO
• Advanced LIGO approved at NSF / NSB (Nov 04) for
  (185M)
• Included in the Bush Administrations budget plan
  released Feb 05 for 2008 start

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Lock Acquisition
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What Limits LIGO Sensitivity?

• Seismic noise limits low frequencies
• Thermal Noise limits middle frequencies
• Quantum nature of light (Shot Noise) limits high
  frequencies
• Technical issues - alignment, electronics,
  acoustics, etc limit us before we reach these
  design goals

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Evolution of LIGO Sensitivity
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Detecting Earthquakes
From electronic logbook 2-Jan-02
An earthquake occurred, starting at UTC 1738.
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Detect the Earth Tide from the Sun and Moon
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Science Runs

A Measure of Progress
Milky Way
Andromeda
Virgo Cluster
NN Binary Inspiral Range
E8 5 kpc
S1 100 kpc
S2 0.9Mpc
S3 3 Mpc
Design 14 Mpc
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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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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 Earths
  motion relative to the Solar System Barycenter,
  intrinsic frequency changes.

• Amplitude modulation due to the detectors
  antenna pattern.

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Two Search Methods

• Frequency domain
• Best suited for large parameter space searches
• Maximum likelihood detection method Frequentist
  approach

• Time domain
• Best suited to target known objects, even if
  phase evolution is complicated
• Bayesian approach

Early science runs --- use both pipelines for the
same search for cross-checking and validation
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Directed Pulsar Limits 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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Directed Pulsar Search
28 Radio Sources
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Upper limit on pulsar ellipticity
NEW RESULT 28 known pulsars NO gravitational
waves e lt 10-5 10-6 (no mountains gt 10 cm
R
.
.
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Ellipticity Limits

• Best upper-limits
• J1910 5959D h0 lt 1.7 x 10-24
• J2124 3358 ? lt 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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Detection of Periodic Sources

• Signature of gravitational wave Pulsars

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

• Amplitude modulation due to the detectors
  antenna pattern.

ALL SKY SEARCH enormous computing challenge
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Einstein_at_Home

• A maximum-sensitivity all-sky search for pulsars
  in LIGO data requires more computer resources
  than exist on the planet.
• The worlds largest supercomputer is arguably
  SETI_at_home
• A 599 computer from Radio Shack is a very
  powerful computational engine.
• Currently runs on a half-million machines at any
  given time.
• With help from the SETI_at_home developers, LIGO
  scientists have created a distributed public
  all-sky pulsar search.

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Einstein_at_Home

• Versions are available for Windows, Mac, Linux.
• How does Einstein_at_home work?
• Downloads a 12 MB snippet of data from
  Einstein_at_home servers
• Searches the sky in a narrow range of frequencies
• Uploads interesting candidates for further
  follow-up
• Screensaver shows where you are currently
  searching in the sky
• We invite all of you to join Einstein_at_Home and
  help us find gravitational waves.

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Einstein_at_Home Usage
Test Version had about 7K Users 5x LIGO computing
capacity OFFICIAL RELEASE on 20-Feb
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Einstein_at_Home Users

• I'm from Germany and was interested in the
  mysteries of the universe since I was a little
  boy. I read lots of magazines about astrophysics
  and astronomy. When I heard about the
  Einstein_at_Home project it was no question for me
  to participate.
• My job is to make original-sized design models of
  new Mercedes-Benz cars, especially the interieur.
  When I don't work I often play keyboards and
  percussions and sing some backing vocals in my
  cover-rock-band "Gilga-Mesh"

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Einstein_at_Home Users

• Hi, my name's John Slattery. I'm a 62 year old
  English teacher, originally from Boston, MA,
  currently living in Santa Fe, New Mexico where
  I'm tutoring, and teaching ESL.
• My hobbies fitness, camping, hiking, reading,
  writing, surfing the Net
• I'm so very new at this I'm not even sure what's
  going on. But it seemed, from the little I could
  understand, to be a worthwhile project.

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Einstein_at_Home Users
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Einstein_at_Home LIGO Pulsar Search using personal
computers BRUCE ALLEN Project Leader Univ of
Wisconsin Milwaukee LIGO, UWM, AEI,
APS http//www.physics2005.org/events/einsteinath
ome/index.html http//einstein.phys.uwm.edu