Searching for gravitational radiation from Scorpius X-1: Limits from the second LIGO science run. Alberto Vecchio on behalf of the LIGO Scientific Collaboration GWDAW10 - UTB, 14th - 17th December, 2005 LIGO - G05xxxx. Outline. Analyses carried out by the LSC Pulsar group
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Searching for gravitational radiation from Scorpius X-1: Limits from the second LIGO science run
Alberto Vecchio
on behalf of the LIGO Scientific Collaboration
GWDAW10 - UTB, 14th - 17th December, 2005
LIGO - G05xxxx
Braking
mechanism
is needed
to explain
lack of
sources
here
Predicted Sco X-1 signal amplitude:
Known parameters:
Sky position (no search over sky)
Period (for T < 1 month)
No spin-down (for T < 1 week)
Search parameters:
Orbit: projected semi-major axis and “time of periapse passage”
Frequency
Possibly eccentricity (we set e = 0 in templates for S2 search)
Number of templates
1018
1014
1012
1010
108
106
104
102
S2 analysis
For Tspan < orbital period, the time of the analysis scales as:
This is a computationally limited search
103 104 105 106
Observation time Tspan /sec
Time transformations:
From SSB time T to detector time t (depends on position in the sky):
From SSB time T to source time tp (depends on orbital parameters)
GW phase (in source frame): monochromatic over the observation time
464 - 484 Hz
604 - 624 Hz
L1
H1
1/50 of the whole parameter space
465 Hz - 466 Hz
Example of expected vs actual distribution of the values of 2F in single interferometer output
L1
“Good” band
“Bad” band (not the worse!)
H1
Illustration of coincidence analysis (orbital filters)
Orbital parameter 2
Orbital parameter 1
Before coincidence
464 - 484 Hz
604 - 624 Hz
Mean value of loudest 2F (excluding 3 disturbed bands) for each 1 Hz band before and after coincidence:
<2 F>L1 = 40.8
<2 F>L1 = 28.6
<2 F>H1 = 45.4
<2 F>H1 = 33.5
After coincidence
614-615 Hz
614-615 Hz
464 - 484 Hz
604 - 624 Hz
Best upper-limit:
h095% = 1.73 (0.02 + 0.16) x 10-22
h095% = 2 x 10-22
Upper limit on ellipticity (assuming Sco X-1 distance of 2.8 kpc):
010-4
10-3
5x10-4
e = 5x10-3
469-470
464-466
614-615
479-480
e = 10-4 e = 5 x 10-4 e = 10-3 e = 5 x 10-3
C = 0.95 C = 0.95 C = 0.88 C = 0.50
For e > 5 x 10-4 the pipeline looses efficiency: the fitting factor of templates with signal is < 1