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Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary Systems

Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary Systems. Andrés C. Rodríguez Louisiana State University M.S. Thesis Defense Thesis Advisor: Professor Gabriela González 6.20.07 LIGO-G070394-00-Z. Outline. LIGO Sources of Gravitational Waves

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Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary Systems

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  1. Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary Systems Andrés C. Rodríguez Louisiana State University M.S. Thesis Defense Thesis Advisor: Professor Gabriela González 6.20.07 LIGO-G070394-00-Z

  2. Outline • LIGO • Sources of Gravitational Waves • Data Analysis for Coalescing Binary Systems • Methods to Reduce False Alarms - 2 Veto, r2 Test • LIGO S3 Primordial Black Hole Search • Conclusions 6.20.07 02

  3. Laser Interferometer Gravitational Wave Observatory (LIGO) s(t) = [Lx - Ly]/L 6.20.07 03

  4. LIGO Siteslsc.org Hanford: two interferometers in same vacuum envelope - 4km (H1), 2km(H2) Livingston: 4km (L1) Generated with Google EarthTM 6.20.07 04

  5. Improved Sensitivity, LIGO Science Runs • S1Aug ‘02 - Sept ‘02 • S2Feb ‘03 - April ‘03 • S3Oct ‘03 - Jan ‘04 • S4Feb ‘05 - March ’05 • S5Nov ‘05 - current 6.20.07 06

  6. Sources of Gravitational Waves • periodic signals: pulsars • •burst signals: supernovae, gamma ray bursts • •stochastic background: early universe, • unresolved sources • compact binary coalescing (CBC) systems: neutron stars, • black holes Crab pulsar (NASA, Chandra Observatory) NASA, WMAP ` 6.20.07 05

  7. Coalescing Binary Systems • General Relativity predicts the decay of the binary • orbit due to the emission of gravitational radiation. • Waveforms can be well approximated by • 2nd order post-Newtonian expansion. • Non -spinning waveforms parameterized by: • » masses: m1,m2, total mass M, or reduced mass  • » orbital phase  & orientation  • » position in the sky: ,  6.20.07 07

  8. Coalescing Binary Systems II • Effective Distance: • Chirp Mass: • Symmetric Mass ratio : 6.20.07 08

  9. Matched Filtering • Data stream searched using matched filtering between • data & template waveform: • Effective Distance: • Matched Filter: • Characteristic Amplitude: • Signal to Noise Ratio (SNR): • Inspiral Trigger: & * 6.20.07 09

  10. Inspiral Coincidence Pipeline • Data Collection • Template Bank Generation: • h(f) • Matched Filter I: z(t), (t), • ask  > * • 1st Coincidence (time, , Mc ) • Matched Filter 2: • 2, r2 Test • 2nd Coincidence (time, , Mc) • Follow Up

  11. Methods to Reduce False Alarms I:2 Veto • , • Inspiral Trigger: • & * *2 6.20.07

  12. Simulated Waveform vs False Alarm 6.20.07 12

  13. Methods to Reduce False Alarms II:r2 Test • Use the r2 time series (2/p) as a method to search for • excess noise. • Impose a higher r2 threshold (r*2) than the search employs. • » Count the number of • time samples (t) • above r*2 in a time • interval (t*) before • inferred coalescence t = 0.9 sec t* r*2 *2 6.20.07

  14. Methods to Reduce False Alarms IIr2 Test Result: S4 BNS Search t = 0.26 sec Simulated Waveforms: 0% falsely dismissed False Alarms: 35%,36% vetoed rd r 6.20.07 14

  15. r2 Test Results: Searches performed by CBC Group in the LSC • r2 test is included in current LIGO searches: • S5 Low Mass (M < 35MSOL) 1 year 6.20.07 15

  16. S3 Primordial Black Hole (PBH) Search I • Black hole composed with mass < 1.0 MSOL is believed to be a primordial black hole (PBH). • They are compact objects may have formed in the early, highly compressed stages of the universe immediately following the big bang. • Speculated to be part of the galactic halo or constituent of dark matter (small fraction). • Binary system composed of two PBH’s will emit gravitational waves that may be detectable by LIGO. • A PBH binary composed of 2 x 0.35 MSOL objects would have a coalescence frequency of 2023Hz and would spend about 22 seconds in LIGO’s sensitive band. 6.20.07 16

  17. S3 PBH Search II • Target Sources: • S3: October 3 - January 09: 2004 • * Numbers in () represent time left • after data used for tuning search.

  18. S3 PBH Search III - Tuning • Coincidence Windows • H1H2 Effective Distance Cut • ,  = 0.45 • Parameters Selected: 6.20.07 18

  19. S3 PBH Search IV - Tuning • Effective SNR: • Combined SNR: 6.20.07

  20. S3 PBH Search V: Result • No triple coincident foreground candidate events or background • events were found. • Number of double coincidences found ( ) consistent with • measured background (+). • c2 6.20.07 20

  21. Conclusions • r2 test greatly reduces rate of false alarms in LIGO • CBC searches. • The r2 test be incorporated into future LIGO searches: • S5 Low Mass (M < 35MSOL) 1 year. • A search for primordial black hole binary systems • (M < 1MSOL) in LIGO’s S3 run was performed with • results consistent with measured background. 6.20.07 21

  22. Thank You! • Prof. Gabriela González • Thesis Committee: Prof. James Matthews, Prof. David Young, Prof. Jorge Pullin • LSU-LIGO Group: Chad, Ravi, Rupal, Prof. Warren Johnson, Jake, Dr. Myungkee Sung, • Prof. Joseph Giaime, Shyang, Andy W., Jeff, Dr. Romain Gouaty • CBC Group: Dr. Duncan Brown, Dr. Stephen Fairhurst, Dr. Eirini Messaritaki, • Prof. Patrick Brady, Dr. Alexander Dietz, Drew Keppel • LSC: Prof. Peter Shawhan, Prof. Alan Weinstein, Prof. Laura Cadonati, Dr. John Whelan, • Prof. Vicky Kalogera, Dr. Bill Kells • LSC and CBC Group for access to LIGO data • LSU Dept. of Physics & Astronomy, NSF, Alfred P. Sloan Foundation • This research has been supported by National Science Foundation grants: • PHY-0135389, PHY-0355289.

  23. Extra Slides

  24. BNS Waveform

  25. PBH Waveform

  26. BBH Waveform

  27. SNR

  28. \xi^2

  29. Injection

  30. Injection vs Trigger

  31. r^2 test

  32. r^2 example

  33. r^2 - S3 BNS

  34. r^2 - S3 PBH

  35. r^2 - S4 BNS

  36. r^2 - S4 PBH

  37. r^2 - S5 BBH epoch 1

  38. Pipeline

  39. S3 PBH - Effective Distance Cut

  40. Effective SNR - S3 PBH

  41. Tuning - S3PBH

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