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LIGO: Towards a Gravitational-Wave Astronomy

LIGO: Towards a Gravitational-Wave Astronomy. Ray Frey, University of Oregon for the LIGO Scientific Collaboration LIGO-G0900437. Introduction Observational results; new directions Enhanced and Advanced LIGO, a worldwide network of GW observatories, and a new window on the cosmos.

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LIGO: Towards a Gravitational-Wave Astronomy

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  1. LIGO: Towards a Gravitational-Wave Astronomy Ray Frey, University of Oregon for the LIGO Scientific Collaboration LIGO-G0900437 • Introduction • Observational results; new directions • Enhanced and Advanced LIGO, a worldwide network of GW observatories, and a new window on the cosmos. 01Jun09 UO

  2. Evidence (indirect) for Gravitational Waves PSR 1913+16 Binary n-star system T=60 ms · · T ~ 8 hr Pulsar period observed over 25 years – Taylor and Hulse 01Jun09 UO

  3. Required GW Sensitivity • GW emission requires time varying quadrupole moment of mass distribution → gravitational-wave strain, h = L/ L • Strain estimate: 01Jun09 UO

  4. h = L/ L : How small is 10-18 m ?

  5. GW Interferometer Principle Michelson interferometer with Fabry-Perot cavity arms. End mirrors are pendula  Freely falling test masses GW strain: h = L/ L 01Jun09 UO

  6. 3 0 3 ( ± 0 1 k 0 m m s ) Laser Interferometer Gravitational-wave Observatory 4 km & 2 km WA MIT Caltech • “LIGO Lab” managed and operated by Caltech & MIT with funding from NSF • LIGO Scientific Collaboration: ~50 institutions, world-wide • Ground breaking 1995 • 1st interferometer lock 2000 • design sensitivity 2005 • Advanced LIGO funded 2008 LA 4 km 01Jun09 UO

  7. LIGO Vacuum Equipment • 1.2 m diameter • Aligned to a mm • Total of 16km fabricated with no leaks • 1 nTorr (!) • few, remote pumps • Cover… 01Jun09 UO

  8. Vacuum tube enclosures test 01Jun09 UO

  9. Length readout and control 01Jun09 UO

  10. Coalescing Compact Binaries NS-NS, BH-BH, BH-NS binary systems Matched filter Template-less Matched filter 01Jun09 UO

  11. Chandra image Model Beating the Crab Spindown (Ap. J. Lett. 683, 45 (2008)) • Crab pulsar’s spin rate is gradually slowing down • The energy goes into EM and GW • All into GW? No. In fact, LIGO limits GW emission to ≤ 4% of total spin-down power • Getting close to spindown sensitivity for several other pulsars 01Jun09 UO

  12. Relic GWs: Results and Prospects Cross-correlate LIGO data streams to estimate energy density in isotropic stochastic GW. 01Jun09 UO

  13. Gamma-ray Bursts BATSE • Long-duration GRBs • Stronger afterglows → z • SNe or “hypernovae” • mean z  2.3 GSFC • Short-duration GRBs • Until 2005, no measured z’s → enter Swift • Now: some z’s → “compact binary mergers” GRB030329 HETE-2 • mergers are efficient GW radiators • much smaller z’s (mean  0.6) Oct 6, 2005 01Jun09 UO

  14. GRB 070201 • GRB 070201 – a short-duration gamma-ray burst with position consistent with M31 (Andromeda) • Such a nearby GRB would have easily been observed by LIGO if due to a binary merger • This hypothesis ruled out at ~99% CL • Alternatives: a GRB behind M31 or an SGR in M31 • Astrophys. J. 681 (2008) 1419 Revised error box: arXiv:0712.1502 01Jun09 UO

  15. Global network of interferometers GEO 600m VIRGO 3 km LIGO 4 km & 2 km TAMA 300m LSC: LIGO+GEO AIGO- R&D facility • Detection confidence • Source polarization • Sky location • Duty cycle • Waveform extraction LIGO 4 km 01Jun09 UO

  16. 2006 2007 2008 2009 2010 2011 2012 2013 2014 The Future: Enhanced and Advanced LIGO Enhanced LIGO (S6) • readout noise; laser power • 2 better sensitivity • commission AdLIGO DC readout with real IFOs • reduce AdLIGO startup time Advanced LIGO • Major upgrades: optics, lasers, suspensions, ... • 10 better sensitivity S5 Run S7? S6 LIGO enhanced LIGO AdvancedLIGO Advanced LIGO funded 4/1/2008 build hardware installation science 01Jun09 UO

  17. hcorr hSQL LIGO as a quantum system • LIGO test masses are K oscillators • Position sensitivity limited by Heisenberg: • Quantum noise limits Advanced LIGO sensitivity over much of band • Radiation pressure + shot noise A. Buonanno and Y. Chen, PRD (2001) • Beating the SQL • Introduce correlation between RP and shot noise (Signal Recycling) • Squeezed light 01Jun09 UO

  18. Advanced LIGO reach (example) NS-NS merger reach BNS sources  Dn n = 2.7 → 3 D ~ 50 Mpc, iLIGO ~ 100 Mpc, eLIGO ~ 500 Mpc, aLIGO aLIGO reach includes millions of large galaxies and hundreds of super-clusters 01Jun09 UO

  19. Prospective rates for binary mergers 01Jun09 UO

  20. The cooling off of the universe… 01Jun09 UO

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