Broadband Search for Continuous-Wave Gravitation Radiation with LIGO Vladimir Dergachev (University...
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![Page 1: Broadband Search for Continuous-Wave Gravitation Radiation with LIGO Vladimir Dergachev (University of Michigan) LIGO Scientific Collaboration APS meeting,](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649cc95503460f94991bcc/html5/thumbnails/1.jpg)
Broadband Search for Continuous-Wave Gravitation
Radiation with LIGO
Vladimir Dergachev(University of Michigan)
LIGO Scientific Collaboration
APS meeting, Dallas April 22-25 2005 DCC: G060180-00-Z
![Page 2: Broadband Search for Continuous-Wave Gravitation Radiation with LIGO Vladimir Dergachev (University of Michigan) LIGO Scientific Collaboration APS meeting,](https://reader036.fdocuments.us/reader036/viewer/2022062407/56649cc95503460f94991bcc/html5/thumbnails/2.jpg)
Challenges of search for CW gravitational waves
● Gravitational waves are weak – need to average over long time periods
● Several parameters to search for: frequency, sky position, spindown, polarization
● Coherent methods are very sensitive, but result in enormous search space size – broadband, all sky search is impractical for large time base
● PowerFlux – place sky-dependent upper limits and detect signals by averaging power. Practical for all-sky broadband searches.
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PowerFlux analysis pipeline
1800secPeriodograms
Noisedecomposition
Linedetection
Dopplershifts
Amplitudemodulation
Detector response
CutOff
Weightedmean
Upper limit
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PowerFlux results
● PowerFlux produces a 95% CL upper limit for a particular frequency, sky position, spindown and polarization.
● Too much data to store, let alone present – the number of sky positions alone is ~10^5 at low frequencies and grows quadratically with frequency
● The upper limit plots show maximum over spindown range, all polarizations and a particular spindown-dependent sky area
● We also present a simple formula that approximates background curve within ±50%
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“S parameter”
Spindown (Hz/s)
Frequency Unit sky position vector
Average detector velocityAverage
detectoracceleration
When S is closer to 0 susceptibility to stationary artifacts increases
Earth orbit angular velocity
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Doppler SkybandsSkyband 0 (good – only exceptionally strong detector artifacts)
Skyband 10 (worst – many detector artifacts)
RA
DEC
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Sample of 95% CL Upper Limits on hlinear=0.5*h0-worst case (sky band 0)
Quoted limit
Poor antenna pattern
Good antenna pattern / noise
Cou
nt
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Corresponding skymap of strain limits(Hanford 4km, 149-149.25 Hz, spindown 0)
Poor antenna pattern
Good antenna pattern
Masked detector artifact (in bad Doppler sideband)
RA
DEC
0
4.73e-24
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One entry per sky point (maximum strain upper limit over 501 frequency bins)
Corresponding Signal-to-Noise Ratios
Cou
nt
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S4 run summary
● Frequency range: 50-1000 Hz
● Spindown range: 0 through -1e-8 Hz/s
● Background (cyan curve) can be described by the following formula:
Here f is frequency in Hz
● Skyband 0 (maximum over which is shown on plots) is defined by
abs(S)>3.08e-9 Hz/s
Strain=4⋅10−26⋅f 0.93⋅10−17
f 3.5
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S4 run resultsLivingston 4km
● Blue – non Gaussian noise● Red - wandering line suspected● Magenta – 60 hz harmonics● Green – 95% CL upper limit
Summary curve
Livingston 4km upper limits are slightly lower than the summary curve, but not as clean in low frequency range
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S4 run resultsHanford 4km
● Blue – non Gaussian noise● Red - wandering line suspected● Magenta – 60 hz harmonics● Green – 95% CL upper limit
Summary curve
Hanford 4km upper limits are slightly higher than the summary curve, but much cleaner in low frequency range
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Summary curve deviation
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Current S5 sensitivity
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Early S5 Hanford 4km Preliminary Results 40-800 Hz (spindown 0)
● Blue – non Gaussian noise● Red - wandering line suspected● Magenta – 60 hz harmonics● Green – 95% CL upper limit
Violin modes – from steel wires that support mirrors
S4 summary curve
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Early S5 Livingston 4km Preliminary Results 40-700 Hz (spindown 0)
60 Hz harmonics greatly mitigated
S4 summary curve
● Blue – non Gaussian noise● Red - wandering line suspected● Magenta – 60 hz harmonics● Green – 95% CL upper limit
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Conclusion
● Low-SNR coincidence algorithm under development
● S5 run is still underway – more data is being collected