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

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Gravitational Wave Detection of Astrophysical Sources

Barry C. BarishCaltech

Neutrino Telescope Venice

24-Feb-05 LIGO-xxx

Crab Pulsar

24-Feb-05 Venice Neutrino Telescope 2

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Einstein’s 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 radiationbinary inspiral

of compact objects


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Einstein’s Theory of Gravitationgravitational waves

0)1

(2

2

22

htc

• 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

)/()/( czthczthh x

• 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

Detectors in space

LISA

Gravitational Wave

Astrophysical Source

Terrestrial detectorsVirgo, LIGO, TAMA, GEO

AIGO


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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

As a wave passes, the arm lengths change in different ways….

…causing the interference pattern

to change at the photodiode

Arms in LIGO are 4km Measure difference in

length to one part in 1021 or 10-18 meters

SuspendedMasses


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Simultaneous Detection

3002 km

(L/c = 10 ms)

Hanford Observatory

Caltech

LivingstonObservatory

MIT


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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 Administration’s 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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An earthquake occurred, starting at UTC 17:38.

From electronic logbook 2-Jan-02

Detecting Earthquakes


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Detect the Earth Tide from the Sun and Moon


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Science Runs

S2 ~ 0.9Mpc

S1 ~ 100 kpc

E8 ~ 5 kpc

NN Binary Inspiral Range

S3 ~ 3 Mpc

Design ~ 14 Mpc

A Measure of Progress

Milky WayAndromedaVirgo Cluster


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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 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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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

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

0

strain

Marginalized Bayesian PDF for

h


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Directed Pulsar Search

28 Radio Sources


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R

R

fIh zz

20

4

2

0 c

G8

moment of inertia tensor

gravitational ellipticity of pulsar

Upper limit on pulsar ellipticity

..

NEW RESULT28 known pulsars

NO gravitational waves

e < 10-5 – 10-6 (no mountains > 10

cm


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EM spin-down upper-limits

LIGO upper-limits from hmax

J1939+2134

S1

S2

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: < 4.5 x 10-6

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


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Detection of Periodic Sources

Signature of gravitational wave Pulsars

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.

ALL SKY SEARCH enormous computing challenge


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Einstein@Home A maximum-sensitivity all-sky search for pulsars

in LIGO data requires more computer resources than exist on the planet.

The world’s largest supercomputer is arguably SETI@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@home developers, LIGO scientists have created a distributed public all-sky pulsar search.


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Einstein@Home

Versions are available for Windows, Mac, Linux.

How does Einstein@home work?

» Downloads a 12 MB ‘snippet’ of data from Einstein@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@Home and help us find gravitational waves.


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Einstein@Home Usage

Test Version had about 7K Users5x LIGO computing capacity

OFFICIAL RELEASE on 20-Feb


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Einstein@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@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@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@Home Users


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Einstein@Home

LIGO Pulsar Search using personal computers

BRUCE ALLENProject Leader

Univ of Wisconsin Milwaukee

LIGO, UWM, AEI, APS

http://www.physics2005.org/events/einsteinathome/

index.html

http://einstein.phys.uwm.edu

Documents

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