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Status of LIGO Data Analysis

Colliding Black Holes Werner Benger, ZIB/AEI. Status of LIGO Data Analysis. Patrick Sutton LIGO Laboratory, Caltech for the LIGO Scientific Collaboration. Outline. LIGO detectors and data-taking runs GW Searches Bursts Inspirals Periodic Sources Stochastic Outlook.

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Status of LIGO Data Analysis

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  1. Colliding Black Holes Werner Benger, ZIB/AEI Status of LIGO Data Analysis Patrick Sutton LIGO Laboratory, Caltech for the LIGO Scientific Collaboration

  2. Outline • LIGO detectors and data-taking runs • GW Searches • Bursts • Inspirals • Periodic Sources • Stochastic • Outlook Sutton TAMA Symp. 2005.02.18

  3. The LIGO ObservatoriesInterferometers are aligned along the great circle connecting the sites • Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov • NASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights). LIGO Hanford Observatory (LHO) H1 : 4 km arms H2 : 2 km arms MIT 3000 km = 10 ms LIGO Livingston Observatory (LLO) L1 : 4 km arms Caltech

  4. LIGO Observatories Hanford Observatory, Washington Two interferometers (4 km and 2 km arms) <- Livingston, LA Livingston Observatory, Louisiana One interferometer (4km) Hanford, WA -> Sutton TAMA Symp. 2005.02.18

  5. LIGO Science Runs 2002 2003 2004 2005 • Interleaved commissioning and engineering/science runs started in 2000: Sutton TAMA Symp. 2005.02.18

  6. Best Sensitivities, S1-S3 LIGO-G030548-02-E Best Inspiral Ranges: S1: L1 0.15Mpc S2: L1 0.9Mpc S3: H1 6.5Mpc design goal: 14Mpc (4km) Sutton TAMA Symp. 2005.02.18

  7. Best Sensitivities in S3 LIGO-G040023-00-E Best Inspiral Ranges: H1: 6.5Mpc H2: 0.8Mpc L1: 1.5Mpc design goal: 14Mpc (4km) Sutton TAMA Symp. 2005.02.18

  8. Data Analysis: Organization • The LIGO Scientific Collaboration (LSC) includes more than 400 individuals and 42 institutions from the USA, Europe, and Asia. • LSC data analysis is organized into four groups by signal type: • Unmodeled Signals (SNe, GRBs, …) • 1. Burst Group • Deterministic Signals: • 2. Binary Inspiral Group • 3. Pulsars/CW Group • Statistical Signals • 4. Stochastic Group Sutton TAMA Symp. 2005.02.18

  9. Searching for Gravitational-Wave Bursts

  10. Gravitational-Wave Bursts • Possible sources: • core-collapse supernovae • perturbed black holes • gamma-ray burst engines • cosmic string cusps • …??? • Poorly modeled - no templates. • Use techniques to detect excess power in data due to generic GWB signals. • Look for simultaneous bursts in all detectors possible supernova waveforms T. Zwerger & E. Muller, Astron. Astrophys. 320 209 (1997) Sutton TAMA Symp. 2005.02.18

  11. Analysis Procedure TFClusters conditioned data 128Hz 1/128s events • Search data for simultaneous excursions in power in each detector. • Methods include TFClusters and Power (Fourier time-frequency), WaveBurst (wavelet domain), BlockNormal and Slope (time domain), … • Apply waveform consistency test (S2, S3; LIGO only) • Background rate from by repeating analysis with artificial time lags between detector sites. • Estimate network sensitivity using coordinated signal injections. • Detection / Upper Limits. • Significant excess of coincidences compared to false alarm rate is possible detection; otherwise set upper limit on GWB rate as a function of signal amplitude. . Sylvestre, PRD 66 102004 (2002) Sutton TAMA Symp. 2005.02.18

  12. Waveform Consistency • New for S2: • Test consistency of waveform as seen by different detectors. • Require cross-correlation of normalized data from pairs of detectors exceed threshold: ? ? ? ? • (“Pearson r-statistic”) • Strong reduction of false alarm rate (~99%) with little loss of efficiency ? ? • Evaluate r over different physical time-lags (+/-10ms) • Evaluate r over range of potential signal durations (<100ms) • Compare distribution of r-values to the null hypothesis • Establish logarithmic confidence of event and threshold on this in order to yield target false alarm rate Cadonati CQG 21 S1695 (2004) Sutton TAMA Symp. 2005.02.18

  13. Efficiency Examples: S3 band-limited white noise New for S3: Testing sensitivity to wide varieties of waveforms. These plots from WaveBurst (wavelet based) code. Preliminary Gaussian- modulated chirps cosmic string cusps Sutton TAMA Symp. 2005.02.18

  14. Upper Limits From S1, S2 Preliminary For narrowband signals near 1kHz S1, S2 LIGO-only, and S2/DT8 LIGO-TAMA searches Slightly lower sensitivity Increased observation time Sutton TAMA Symp. 2005.02.18

  15. Inverse Problem SNR ~ 20 burst, LIGO-GEO Network latitude longitude New for S4?: • Methods of determining sky position (q,f) and h+(t), hx(t) for GWB being implmented • Requires detectors at 3+ sites. • eg: Gursel & Tinto, PRD 40 3884 (1989) Sutton TAMA Symp. 2005.02.18

  16. Other Burst Searches(in progress) • LIGO-TAMA joint burst search using S2/DT8 data • Aimed at high-frequency signals (700-2000 Hz frequency content) • Require 3- or 4-way coincident triggers • Analysis complete, publication in preparation • LIGO-only S3 analysis: • Similar to S2 search, but using improved WaveBurst search method • Efficiency evaluated for a wide range of possible signals • Analysis complete early 2005 • LIGO-GEO S3 analysis: • Aiming search at high-frequency signals (700-2000 Hz) • LIGO-GRB coincidence S2/S3 analysis: • Use cross-correlation method, statistical analysis of the ensemble • New searches: • LIGO-AURIGA in S3: Methodology building for IFO-bar coincidence analyses • LIGO-Virgo: Mock Data challenge • New methods for “all-sky” search: Excess Power, Q-pipeline • New statistical criteria and method for interpreting data • Template-based searches for modeled waveforms (cosmic strings, supernovae) Sutton TAMA Symp. 2005.02.18

  17. Searching for Binary Inspirals

  18. Binary Inspiral Searches • Targets: Chirp signals from inspiralling compact-object binaries: • BH-BH (0.1-1 M๏) “MACHOs” • NS-NS (1-3 M๏) • BH-BH (3-10 M๏) • Sensitive to GW emission from last several seconds/minutes of inspiral. • NS binaries are known to exist! • PSR B1913+16, PSR B1534+12, PSR J0737-3039 • Initial LIGO has a chance to see them (up to ~1/4yr to 20Mpc for NS-NS, up to ~1/2yr to 100Mpc for BH-BH) Sutton TAMA Symp. 2005.02.18

  19. S1 Search • NS-NS binaries with component masses between 1 and 3 M๏ • Sensitive to inspirals in Milky Way: • L1 ~175 kpc, H1 ~46 kpc (1.4-1.4 M๏, optimally oriented, r>8) • Observation time: • 236 hours ( L1 and/or H1 running) • No coincident inspiral signals found • Loudest event due to photodiode saturation. • Upper limit from “loudest event statistic”: Rate < 170/yr/MWEG • Comparable to TAMA result <120/yr/MWEG LIGO Scientific Collaboration (B. Abbott et. al.), ‘Analysis of LIGO Data for Gravitational Waves from Binary Neutron Stars’, PRD 69 122001 (2004) Sutton TAMA Symp. 2005.02.18

  20. S2 Search • Observation time: 355 hours • Use only 2-site data (when L1 and at least one of H1, H2 are operating) • The remaining data are used in coincidence searches with TAMA (S2) and GEO (S3)  in progress Sutton TAMA Symp. 2005.02.18

  21. S2 Range S2: Small increase in number of galaxies for ~10x increase in range! Sutton TAMA Symp. 2005.02.18

  22. S2 Pipeline Sutton TAMA Symp. 2005.02.18

  23. S2 Pipeline: Details h “Chirp” waveform • Since waveform is known, use Wiener optimal matched filtering in frequency domain • Templates: non-spinning 2.0 post-Newtonian, placed for maximum 3% SNR loss. • Require coincident detection (time, mass, effective distance), also apply chi-squared test. • Cluster triggers within duration of each template. Sutton TAMA Symp. 2005.02.18

  24. S2 Results < 50 /yr /MWEG • No coincidences that looked like inspirals. • “Loudest event statistic” upper limit: Preliminary Sutton TAMA Symp. 2005.02.18

  25. Other Inspiral Searches • Binary Black Hole MACHO Search using S2 & S3 data • Binaries with component masses between 0.2 and 1 M๏ • S2 analysis complete, paper being drafted: Sutton TAMA Symp. 2005.02.18 chirp mass (Mo)

  26. Other Inspiral Searches • BNS inspiral search: Joint analysis of LIGO S2 + TAMA DT8 • See poster by Hirotaka Takahashi. • Use rest of LIGO S2 data (~700 hours), requiring coincidence with TAMA • BNS inspiral search: Search using LIGO+GEO S3 data • Visible range: H1: ~6.8Mpc, L1: ~2.2 Mpc, H2: ~1.5 Mpc, GEO: ~45 kpc • Binary Black Hole Search (3 M๏< M < 10 M๏) • Waveforms not well known, no population model • Search using non-spinning BCV detection templates (gr-qc/0205122) • New searches under development • Spinning binary black hole search • Inspiral-burst-ringdown search • GRB coincidence analysis • LIGO-Virgo mock data challenges Sutton TAMA Symp. 2005.02.18

  27. (NASA/CXC/SAO) Searching for Periodic Signals

  28. Periodic Signals • Spinning neutron stars are known to exist! • If their rotation is non-axisymmetric, they will emit gravitational waves • Signal depends on many parameters: frequency f, spindown df/dt, sky coordinates (, ), strain amplitude h0, spin-axis inclination , phase & polarization , . Many templates! Need computationally efficient methods. • Several searches in progress • Known pulsars: phase and amplitude functions are known. • All-sky, wide parameter search for unknown spinning compact objects • Variety of algorithms and search approaches Sutton TAMA Symp. 2005.02.18

  29. Known Neutron Stars • Time-domain searches for GWs from known isolated pulsars • S1: Upper limit on PSR J1939+2134: • h0 < 1.4 x 10 -22 • e < 2.9 x 10-4 • Phys Rev D 69, 082004 (2004) • S2 analysis: • The 28 pulsars with f > 50 Hz for which search parameters are known “exactly” • gr-qc/0410007, submitted to PRL • S3 analysis: • All ~110 pulsars with f > 25 Hz, including those in binaries Sutton TAMA Symp. 2005.02.18

  30. S2 Results (submitted to PRL) • Typical strains O(10-24). • Lowest 95% bound 1.7 x 10-24 (J1910-5959D) • Typical ellipticities O(10-5) • Lowest bound on e = 4.5 x 10-6 (J2124-3358) • Crab pulsar: • h0 = 4.1 x 10-23 • e = 2.1 x 10-2 (~30 times spin-down upper limit) Sutton TAMA Symp. 2005.02.18

  31. F-statistic (Jaronowski, Krolak, & Schutz, PRD 58,1998) frequency domain analyses over O(10h) of S2 data with optimal sensitivity: All sky, broad band (~ 300 Hz ) search for isolated neutron stars. Preliminary upper limits at the 10-22 - 10-23 level Targeted search on Sco X-1 (accreting neutron star in a binary system) using 6 hours of S2 data Add other LMXBs in future, using hierarchical schemes Other Coherent Searches (Artist’s impression: NASA) Sutton TAMA Symp. 2005.02.18

  32. Incoherent Searches • Computationally efficient. • Use to probe a wide parameter space. • Frequency-domain. • Based on computing short-duration power spectra. • Add spectra after frequency “slide” to correct for Doppler shift, spindown. • Look for peaks in summed power • Three variants: • Hough transform (S2: all sky, ~200Hz band, one spin-down parameter, analysing all data) • Stack-slide (planned for S3) • PowerFlux (planned for S3) stack-slide schematic Sutton TAMA Symp. 2005.02.18

  33. Einstein@home • Like SETI@home, but for LIGO/GEO data. • Goal: pulsar searches using ~1 million clients for a blind hierarchical search. • Help from APS with publicity, web site, graphics. • Use infrastructure from SETI@home for the distributed computing parts (BOINC). • Support for Windows, Mac OSX, Linux clients. • In testing phase. Sutton TAMA Symp. 2005.02.18

  34. Searching for Stochastic Signals

  35. Stochastic GW Background • Random GW signal arising from: • Cosmological processes, such as inflation, phase transitions, or cosmic strings • Superposition of weak signals from many astrophysical sources • Characterized by fraction of closure density of the universe in GWs: • Big-bang nucleosynthesis limit on cosmological background: W < 10-5 Sutton TAMA Symp. 2005.02.18

  36. The Search Statistic • Cross-correlate the output of pairs of detectors. • Optimal filter depends on geometry, favors low frequencies • falls rapidly for frequencies above 1/(separation distance) g(f) f (Hz) Sutton TAMA Symp. 2005.02.18

  37. Stochastic Searches • S1: Derived upper limits from each pair of LIGO detectors • “Analysis of first LIGO science data for stochastic gravitational waves” Phys. Rev. D 69, 122004 (2004) • Best limit: W < 23 (from H1-L1 pair) • S2: Data used as practice for S3. • Strong improvement in sensitivity • New treatment of PSDs to avoid bias in cross-correlations: use data from neighboring time to construct optimal filter. • Apply vetoes for noise non-stationarity. • Observed properties of the search statistics fit expected ones after correcting for biases and known systematics. Sutton TAMA Symp. 2005.02.18

  38. S2 H1-L1 Analysis PRELIMINARY Sutton TAMA Symp. 2005.02.18

  39. S3 H1-L1 Analysis S3 analysis in progress. Cumulative error estimate (+3s) as a function of run time. Should be sensitive to W ~ O(10-3) Sutton TAMA Symp. 2005.02.18

  40. x 1000 better! x 10-100 better! PRELIMINARY LIGO Limits on gwh1002 Sutton TAMA Symp. 2005.02.18

  41. Other stochastic searches • L1-ALLEGRO cross-correlation (S2) • ALLEGRO bar detector close (40 km) to LIGO-Livingston - better overlap g(f) • Can modulate L1-ALLEGRO GW signal by rotating bar (off-source experiment!) • Underway - expected S2 sensitivity of Wgw(f) ~ 10 • Targeted search • Look for broadband gravitational waves coming from a particular point on the sky using IFO-IFO cross-correlations, properly delayed to point at, e.g., the Virgo cluster • Currently being planned • Search for (f) ~ n(f/f0)n Sutton TAMA Symp. 2005.02.18

  42. Summary • Science analyses of LIGO data are well under way • S1 results demonstrated analysis techniques • S2 analyses are nearing completion; preliminary results public • Improved methods and instruments • S3 analyses well under way • As we are approaching design sensitivity and duty cycle … • Perform analyses close to real time • Operate as part of an international network of detectors • Get ready for detections! Sutton TAMA Symp. 2005.02.18

  43. Science Run Papers • The LIGO Scientific Collaboration published four data analysis papers using data from the S1 run: • “Setting upper limits on the strength of periodic gravitational waves using the first science data from the GEO600 and LIGO detectors”Phys. Rev. D 69, 082004 (2004) • “First upper limits from LIGO on gravitational wave bursts”Phys. Rev. D 69, 102001 (2004) • “Analysis of LIGO data for gravitational waves from binary neutron stars” Phys. Rev. D 69, 122001 (2004) • “Analysis of first LIGO science data for stochastic gravitational waves” Phys. Rev. D 69, 122004 (2004) • Also: • “Detector Description and Performance for the First Coincidence Observations between LIGO and GEO”Nuclear Instruments and Methods A 517, 154 (2004) Sutton TAMA Symp. 2005.02.18

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