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From Initial to Advanced gravitational wave interferometers: results, challenges and prospects.

From Initial to Advanced gravitational wave interferometers: results, challenges and prospects. Sergey Klimenko, University of Florida for the LIGO and Virgo collaborations. Credit: AEI, CCT, LSU. Gravitational Waves.

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From Initial to Advanced gravitational wave interferometers: results, challenges and prospects.

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  1. From Initial to Advancedgravitational wave interferometers:results, challenges and prospects. Sergey Klimenko, University of Floridafor the LIGO and Virgo collaborations Credit: AEI, CCT, LSU

  2. Gravitational Waves • space-time perturbations propagating at the speed of light predicted by A.Einstein in 1916 as part of his theory of General Relativity • J.Weber: ”When I decided to search for gravitational waves some 14 years ago, most physicists applauded ourcourage@,but felt that success – detection of gravitational radiation – would require a century of experimental work.” (Popular Science May 1972) @W.Churchill: “Courage is going from failure to failure without losing enthusiasm” • after a decade of experiments with the initial (1G) GW interferometers, the advanced (2G) detectors are targeting detection of GWs in ~2016 – 100 years after their prediction.

  3. Gravitational Waves: the evidence Emission of gravitational waves Hulse & Taylor PSR 1913 + 16 Neutron Binary System Separated by 106miles, m1 = 1.4m; m2 = 1.36m; • Prediction from general relativity • spiral in by 3 mm/orbit • merge in 300 million years • time of periastron relative to that • expected if the orbital separation • remained constant.

  4. LIGO, VIRGO, GEO, TAMA: breakthrough in the GW experiment GW Detectors Interferometers wideband (~10000 Hz) Bars narrowband (~1Hz) recent improvements (~10Hz) ALLEGRO, AURIGA, EXPLORER, NAUTILUS, NIOBE, … 2008 1968 UF graduate student Kate Dooley inspecting a LIGO optic. J.Weber working on the bar

  5. Sensitivity of 1G Interferometers strain noise:

  6. Hanford, WA (LHO) H1: 4km x 4km H2: 2km x 2km Livingston, LA (LLO) L1: 4km x 4km LIGO Observatory • Initial LIGO detectors (1G) were in operation for a decade • 6 data taking runs (~1.5 years of 2D live time) • reached its design sensitivity during the S5 run: 2005-2007 Virgo detector joined in May 2007 (VSR1 run) • run enhanced configuration during the s6 run: 2009 – 2010 • decommissioned in October 2010 • started to constrain source models (analysis of data continues) • paved road for aLIGO 2G detectors • established conceptually new GW data analysis • began integration of GW experiment and astronomy

  7. supernovae binary neutron stars NS-NS gamma ray bursts binary black holes pulsars Casey Reed, Penn State Credit: AEI, CCT, LSU soft gamma repeaters Credit: Chandra X-ray Observatory and other violent astrophysical sources.. Gravitational Wave Sources

  8. BH ringdown merger: NR GR inspiral: PN GR Compact Binary Coalescence: NS-NS • NS-NS – LIGO standard candle (1G horizon ~30Mpc)) • large expected signal, inspiral in the sweet spot (100-300Hz) • challenges: get physics at merger phase (~1.5kHz) • CL – cumulative luminosity (370L10) • T – observation time (~1 year) • measured rate limit: <3.2 / year: • expected rates: ~0.01 / year L10 = 1010 L,B (1 Milky Way = 1.7 L10)

  9. Black Holes

  10. BH binary coalescence: BH-BH & BH-NS Background: S5/VSR1 burst search event strength M<20Mo • BH searches • low mass BH & NS (<25Mo)  search with inspiral templates • high mass BH-BH (25-100Mo)  search with IMR templates • massive BH-BH (100-500Mo)  burst searches • high mass CBC (>25Mo) are better detected via their merger and ring-down waves (in progress). Challenges: • need merger waveforms (Numerical Relativity calculations) • background due to non-stationary detector noise

  11. Low Mass CBC BH search BH-BH NS(1.35Mo)-BH • S5/VSR1 run (T~1year): PRD 82 (2010) 102001 • Measure rate limits: • Expected rates BH(5Mo)-BH(5Mo): CL = 8300L10 BH(5Mo)-NS: CL = 1600L10 CQG. 27 (2010) 173001

  12. All-Sky Burst Searches PRD 72(2005) 062001 CQG 24(2007) 5343-5369 CQG 25(2008) 245008 • model independent, however sensitive to a wide class of sources: binary mergers, SN, SGR,.. • use ad-hoc waveforms (Sine-Gaussian, Gaussian, etc.) to determine detection sensitivity • Challenges: affected by detector glitches  need smart network search algorithms and very detail understanding of the detector noise Sine-Gaussian waveforms, Q=8.9

  13. Supernova • GW from supernova • Several Core-Collapse SN Mechanisms • Direct “live” information from the supernova engine. Karachentsev et al. 2004; Cappellaro et al. 1999 1/50 yr - Milky Way Ott, et al.

  14. Mass equivalent sensitivity • strain sensitivity can be converted to energy sensitivity assuming isotropic GW emission Capable to detect burst sources out to Virgo cluster if EGW is few % of Mo For lower energy output (like SNs, which also produce HF signals) need advanced detectors to see beyond our Galaxy 16Mpc 10kpc

  15. short GRB070201 • Sky location consistent with Andromeda (M31) • Possible progenitors: • NS-NS or BH-NS merger • Soft Gamma Repeater • Inspiral search: • excludes binary progenitor in Andromeda at >99% confidence level • Exclusion of merger at larger distances • Burst search: • Cannot exclude a Soft Gamma Repeater (SGR) at M31 distance • Upper limit: EGW<8x1050 ergs (<4x10-4 Moc2) no gravitational waves detected APJ 681 (2008) 1419 25% 50% 75% 90% DM31≈770 kpc more GRB results: APJ 715 (2010) 1438 search for GWs from137 GRBs in S5

  16. GWs from 116 known pulsars APJ. 713 (2010) 671 limits on GW amplitude S3/S4 10-25 S5

  17. Beating the Crab Pulsar Spin Down Limit Astrophys. J. 713 (2010) 671 • Young and rapidly spinning down • GW frequency 59.6 Hz • Experimental limits • GW strength: • h(95%CL) < 2.0 x 10-25 • the spin down limit (assuming restricted priors) • ellipticity limit: e < 1.0 x 10-4 • GW energy upper limit: < 2% of radiated energy is in GWs

  18. Stochastic Background Nature., V460: 990 (2009). LIGO S5 result: W0 < 6.9 x 10-6

  19. Multimessenger Astronomy • observation and measurement of the same astrophysical event by different experiments • better confidence of GW event • extract physics of source engine • Externally triggered strategy • routinely used by LIGO • Look-Up strategy • close integration with astronomy: search for EM counterpart with optical and radio telescopes • need low latency (few min) source localization from GW detectors • rely on source reconstruction • In 2009-2010 LIGO and Virgo carried out first EM followup experiments  analysis in progress

  20. Challenges of GW reconstruction • If detection of GW signals is hard, the reconstruction • even harder and not really addressed yet. • incomplete or no source models • dependence on antenna patterns & detector noise • dependence on GW waveforms and polarization state • reconstruction bias due to algorithmic assumptions • reconstruction bias due to calibration errors • high computational cost • ….there are many ways to get it wrong • need smart algorithms • eventually need more detectors

  21. Source localization method • Based on triangulation (t1,t2,t3,..) • 3 or more sites • Coupled to reconstruction of GW waveforms  coherent analysis of data from all detectors in the network. t1 t3 t2 Probability map error region

  22. Antenna patterns & noise • network sensitivity: • network SNR • detectors with small fkdo not contribute to reconstruction • effectively deal with 2 detector network  lose triangulation • need more than 3 sites for robust reconstruction LIGO Virgo

  23. Waveforms & polarization V1, L1, H1 • For linearly polarized signal effectively lose a detector • For signals with random polarization, recover reconstruction due to the 2nd polarization • This effect strongly depends on the sky location additional 4th site solves the problem Simulated signal (SG235Q9) with linear polarization accuracy, degrees simulated signal (WNB 250 Hz) with two random polarizations

  24. 2G (advanced) detectors aVIRGO aLIGO LCGT • x10 better sensitivity than for 1G • aLIGO Is being constructed  start operation in 2014-2015 • aVirgo will emerge in about the same time after a series of upgrades which are in progress. • hopefully LIGO-A and LCGT will be constructed  huge increase in scientific output, make GW astronomy a reality. LIGO-Australia (LIGO-A)

  25. LIGO goes south? • Plans for relocation of one H detector to Australia, Gingin • 5-10 times better sky resolution – compatible with FOV of telescopes • conditional approval from NSF committee report at https://dcc.ligo.org/public/0011/T1000251/001/ Physics Today, Dec, 2010 LHHV LHHV LHVA latitude Error angle in degrees LHVA network SNR longitude

  26. NS-NS 20-200 y-1 SN 0.02-0.5 y-1 BH-BH 20-2000 y-1 2G Astronomical Reach Class. Quantum Grav. 27 (2010) 173001 x10 better amplitude sensitivity x1000rate=(reach)3 CQG. 27 (2010) 173001

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