Gravitational Wave Detection of Astrophysical Sources Barry C
Gravitational Wave Detection of Astrophysical Sources Barry C. Barish Caltech Crab Pulsar - LIGO-xxx 24 -Feb-05 Venice Neutrino Telescope Venice 24 -Feb-05
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 radiation binary inspiral of compact objects - 24 -Feb-05 Venice Neutrino Telescope 2
Einstein’s 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. - 24 -Feb-05 Venice Neutrino Telescope 3
Detection of Gravitational Waves Gravitational Wave Astrophysical Source Terrestrial detectors Detectors in space Virgo, LIGO, TAMA, GEO AIGO LISA - 24 -Feb-05 Venice Neutrino Telescope 4
Gravitational Waves in Space LISA - Three spacecraft, each with a Y-shaped payload, form an equilateral triangle with sides 5 million km in length. 24 -Feb-05 Venice Neutrino Telescope 5
LISA The diagram shows the sensitivity bands for LISA and LIGO - 24 -Feb-05 Venice Neutrino Telescope 6
Detecting a passing wave …. Free masses - 24 -Feb-05 Venice Neutrino Telescope 7
Detecting a passing wave …. Interferometer - 24 -Feb-05 Venice Neutrino Telescope 8
Interferometer Concept l Laser used to measure § Arms in LIGO are 4 km relative lengths of two § Measure difference in orthogonal arms length to one part in 1021 or 10 -18 meters …causing the interference pattern to change at the photodiode As a wave Suspended passes, the Masses arm lengths change in different ways…. - 24 -Feb-05 Venice Neutrino Telescope 9
Simultaneous Detection Hanford Observatory MIT (L 300 /c 2 = km 10 m s) Caltech Livingston Observatory - 24 -Feb-05 Venice Neutrino Telescope 10
LIGO Livingston Observatory - 24 -Feb-05 Venice Neutrino Telescope 11
LIGO Hanford Observatory - 24 -Feb-05 Venice Neutrino Telescope 12
LIGO Goals and Priorities Interferometer performance l » Integrate commissioning and data taking » Obtain one year of integrated data at h = 10 -21 by 2008 Physics results from LIGO I l » Initial upper limit results by early 2003 » First search to begin in 2005 » Reach LIGO I goals by 2008 Advanced LIGO l » Advanced LIGO approved at NSF / NSB (Nov 04) for ($185 M) » Included in the Bush Administration’s budget plan released Feb 05 for 2008 start - 24 -Feb-05 Venice Neutrino Telescope 13
Lock Acquisition - 24 -Feb-05 Venice Neutrino Telescope 14
What Limits LIGO Sensitivity? l Seismic noise limits low frequencies l Thermal Noise limits middle frequencies l Quantum nature of light (Shot Noise) limits high frequencies l Technical issues alignment, electronics, acoustics, etc limit us before we reach these design goals - 24 -Feb-05 Venice Neutrino Telescope 15
Evolution of LIGO Sensitivity - 24 -Feb-05 Venice Neutrino Telescope 16
Detecting Earthquakes From electronic logbook 2 -Jan-02 An earthquake occurred, starting at UTC 17: 38. - 24 -Feb-05 Venice Neutrino Telescope 17
Detect the Earth Tide from the Sun and Moon - 24 -Feb-05 Venice Neutrino Telescope 18
Science Runs Milky Way Virgo Andromeda Cluster A Measure of Progress NN Binary Inspiral Range E 8 ~ 5 kpc S 1 ~ 100 kpc S 2 ~ 0. 9 Mpc S 3 ~ 3 Mpc Design ~ 14 Mpc - 24 -Feb-05 Venice Neutrino Telescope 19
Astrophysical Sources l Compact binary inspiral: “chirps” » NS-NS waveforms are well described » BH-BH need better waveforms » search technique: matched templates l Supernovae / GRBs: “bursts” » burst signals in coincidence with signals in electromagnetic radiation » prompt alarm (~ one hour) with neutrino detectors l Pulsars in our galaxy: “periodic” » search for observed neutron stars (frequency, doppler shift) » all sky search (computing challenge) » r-modes l - Cosmological Signals background” 24 -Feb-05 “stochastic Venice Neutrino Telescope 20
Detection of Periodic Sources l 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. - 24 -Feb-05 Venice Neutrino Telescope 21
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 - 24 -Feb-05 Venice Neutrino Telescope 22
Directed Pulsar Limits on Strain Crab pulsar S 1 J 1939+2134 J 1910 – 5959 D: 1 Marginalized Bayesian PDF for h PDF h 95 S 2 0 strain Red dots: pulsars are in globular clusters - cluster dynamics hide intrinsic spindown properties Blue dots: field pulsars for which spin-downs are known h 0 = 1. 7 x 10 -24 - 24 -Feb-05 Venice Neutrino Telescope 23
Directed Pulsar Search 28 Radio Sources - 24 -Feb-05 Venice Neutrino Telescope 24
Upper limit on pulsar ellipticity moment of inertia tensor gravitational ellipticity of pulsar NEW RESULT 28 known pulsars NO gravitational waves . . 24 -Feb-05 R e < 10 -5 – 10 -6 (no mountains > 10 cm Venice Neutrino Telescope 25
Ellipticity Limits Best upper-limits: • J 1910 – 5959 D: h 0 < 1. 7 x 10 -24 • J 2124 – 3358: < 4. 5 x 10 -6 How far are S 2 results from spindown limit? Crab: ~ 30 X LIGO upper-limits from hmax J 1939+2134 S 1 S 2 EM spin-down upper-limits - 24 -Feb-05 Venice Neutrino Telescope Red dots: pulsars are in globular clusters - cluster dynamics hide intrinsic spin-down properties Blue dots: field pulsars for which spin-downs are known 26
Detection of Periodic Sources Signature of gravitational wave Pulsars l § 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 - 24 -Feb-05 Venice Neutrino Telescope 27
Einstein@Home l A maximum-sensitivity all-sky search for pulsars in LIGO data requires more computer resources than exist on the planet. l 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 allsky pulsar search. l - 24 -Feb-05 Venice Neutrino Telescope 28
Einstein@Home l Versions are available for Windows, Mac, Linux. l 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. l - 24 -Feb-05 Venice Neutrino Telescope 29
Einstein@Home Usage Test Version had about 7 K Users 5 x LIGO computing capacity OFFICIAL RELEASE on 20 -Feb - 24 -Feb-05 Venice Neutrino Telescope 30
Einstein@Home Users l l 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-rockband "Gilga-Mesh" - 24 -Feb-05 Venice Neutrino Telescope 31
Einstein@Home Users l l l 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. - 24 -Feb-05 Venice Neutrino Telescope 32
Einstein@Home Users - 24 -Feb-05 Venice Neutrino Telescope 33
Einstein@Home LIGO Pulsar Search using personal computers BRUCE ALLEN Project Leader Univ of Wisconsin Milwaukee LIGO, UWM, AEI, APS http: //www. physics 2005. org/events/ einsteinathome/index. html - 24 -Feb-05 http: //einstein. phys. uwm. edu 34 Venice Neutrino Telescope
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