Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary Systems
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Transcript of Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary Systems
Reducing False Alarms in Searches for Gravitational Reducing False Alarms in Searches for Gravitational Waves from Coalescing Binary SystemsWaves from Coalescing Binary Systems
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Andrés C. RodríguezLouisiana State University
M.S. Thesis Defense Thesis Advisor: Professor Gabriela González
6.20.07LIGO-G070394-00-Z
• 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
OutlineOutline
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Laser Interferometer Gravitational Wave Observatory (LIGO)Laser Interferometer Gravitational Wave Observatory (LIGO)
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s(t) = [Lx - Ly]/L
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LIGO SitesLIGO Siteslsc.orglsc.org
Hanford: two interferometers in same vacuum envelope - 4km (H1), 2km(H2)
Livingston: 4km (L1)
Generated with Google EarthTM6.20.07 04
Improved Sensitivity, Improved Sensitivity, LIGO Science RunsLIGO Science Runs
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• S1 Aug ‘02 - Sept ‘02
• S2 Feb ‘03 - April ‘03
• S3 Oct ‘03 - Jan ‘04
• S4 Feb ‘05 - March ’05
• S5 Nov ‘05 - current
7/9/2003 `LIGO Scientific Collaboration - Amaldi 2003
Sources of Gravitational WavesSources 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
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Crab pulsar (NASA, Chandra Observatory)
NASA, WMAP
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• 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: ,
Coalescing Binary SystemsCoalescing Binary Systems
• Effective Distance:
• Chirp Mass:
• Symmetric Mass ratio :
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Coalescing Binary Systems IICoalescing Binary Systems II
Matched Filtering Matched Filtering
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*
• Data stream searched using matched filtering between data & template waveform:
Effective Distance:
• Matched Filter:
• Characteristic Amplitude:
• Signal to Noise Ratio (SNR):
• Inspiral Trigger: &
• 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
Inspiral Inspiral Coincidence Coincidence
PipelinePipeline
*
,
Inspiral Trigger:
&
Methods to Reduce False Alarms I:Methods to Reduce False Alarms I:22 Veto Veto
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*2
Simulated Waveform vs False AlarmSimulated Waveform vs False Alarm
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Methods to Reduce False Alarms II:Methods to Reduce False Alarms II:rr22 Test Test
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• 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
Methods to Reduce False Alarms IIMethods to Reduce False Alarms IIrr2 2 Test Result: S4 BNS SearchTest Result: S4 BNS Search
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Simulated Waveforms: 0% falsely dismissedFalse Alarms: 35%, 36% vetoed
rd r
t = 0.26 sec
rr22 Test Results: Test Results: Searches performed by CBC Group in the LSCSearches performed by CBC Group in the LSC
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• r2 test is included in current LIGO searches: S5 Low Mass (M < 35MSOL) 1 year
• 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.
S3 Primordial Black Hole (PBH) Search IS3 Primordial Black Hole (PBH) Search I
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• Target Sources:
S3: October 3 - January 09: 2004
* Numbers in () represent time left after data used for tuning search.
S3 PBH Search IIS3 PBH Search II
• Coincidence Windows
• H1H2 Effective Distance Cut
, = 0.45
• Parameters Selected:
S3 PBH Search III - TuningS3 PBH Search III - Tuning
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• Effective SNR:
• Combined SNR:
S3 PBH Search IV - TuningS3 PBH Search IV - Tuning
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S3 PBH Search V: ResultS3 PBH Search V: Result
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• No triple coincident foreground candidate events or background events were found.• Number of double coincidences found ( ) consistent with measured background (+).
c2
• 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.
ConclusionsConclusions
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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.
Thank You!Thank You!
Extra SlidesExtra Slides
BNS WaveformBNS Waveform
PBH WaveformPBH Waveform
BBH WaveformBBH Waveform
SNRSNR
\xi^2\xi^2
InjectionInjection
Injection vs TriggerInjection vs Trigger
r^2 testr^2 test
r^2 exampler^2 example
r^2 - S3 BNSr^2 - S3 BNS
r^2 - S3 PBHr^2 - S3 PBH
r^2 - S4 BNSr^2 - S4 BNS
r^2 - S4 PBHr^2 - S4 PBH
r^2 - S5 BBH epoch 1r^2 - S5 BBH epoch 1
PipelinePipeline
S3 PBH - Effective Distance CutS3 PBH - Effective Distance Cut
Effective SNR - S3 PBHEffective SNR - S3 PBH
Tuning - S3PBHTuning - S3PBH