1. Data Analysis report November, 2009 Gianluca M Guidi
Università di Urbino and INFN Firenze
for the Virgo Collaboration
November, 2009
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2. STAC - Data Analysis Report
LSC-Virgo scientific groups are concluding the searches on S5/VSR1 data. Papers with the scientific results are being written and circulated inside the scientific groups and/or the collaborations:
All-sky Low Mass CBC
All-sky High Mass CBC
GRB –CBC
All-sky Bursts
GRB – Bursts paper:
“Search for gravitational-wave bursts associated with gamma-ray bursts using data from LIGO Science Run 5 and Virgo Science Run 1 “
has been submitted to ApJ
Virgo is strongly working on Data Qualities, vetoes and noise hunting for S6/VSR2. This is fundamental as glitches are one of the main limiting factor of any search.
S6/VSR2 analysis is on-going with a strong partecipation of Virgo
November, 2009
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Contents
Here we present some highlights
the all-sky search for Bursts
the all-sky search Low Mass CBC
A quick look at the status of the work on DQ, vetoes and noise
All the results are preliminary and not still vetted to be diffused outside the LSC-Virgo collaborations
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All-sky Bursts S5/VSR1
The all-sky paper is ready and has already circulated in the collaborations
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All-sky Bursts S5/VSR1
We used simulated signals to evaluate the sensitivity of the search:
NS gravitational collapse to BH and BH ringdown
simulated waveforms (Baiotti et al.). These are
signals with a high frequency content, in the
region where the IFOs are less sensitive
Obtain directely the efficiency of the search as a
function of the distance
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All-sky Bursts S5/VSR1
Sine-Gaussian waveforms
Gaussian waveforms
Harmonic ringdown signals
Band-limited white noise signals
Merger of two
Black Holes
Baker et al Class. Quant. Grav. 24, S25-S31 (2007)
Neutron-star
fundamental modes,
Supernova
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All-sky Bursts S5/VSR1
Obtain the sensitivity of the search as a function of hrss:
hrss50% as low as
5.6e-22 Hz-1
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8. All-sky Bursts S5/VSR1 Astrophysical sensitivities of the search:
Amount of mass converted in GW detected with 50% efficiency:
2.1e-8 Mo at 10 kpc
0.05 Mo at 16 Mpc
(Virgo cluster)
f0=153 Hz
Q=9
Core-collapse supernovae
f0=940 Hz
High Q
Could emit 8e-5 Mo (optimistic limit)
Detectable at
30 kpc
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All-sky Bursts S5/VSR1
Upper Limits on the rate R
Combined S5y1 and S5y2/VSR1 UL at 90% confidence level for strong GW
90% UL on the rate density R
for SG, standard candle
with EGW = Mo c2
2.0 – 2.2 yr-1
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10. All-sky Bursts S5/VSR1 Astrophysical interpretation: Mtot = 100 Mo
Limit on the rate density of binary BHs mergers
3.6%Mtot in GW
f = 16 kHz (Mo/Mtot)
[Berti 07; Hannam 09]
Mtot = 100 Mo
R  R (Mo/MGW)3/2
R = 9e-8 yr-1 Mpc-3
Consistent with the theoretical rates from population
synthesis models
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Low Mass CBC S5/VSR1
The search is near conclusion. A first draft of the paper is being circulated in the CBC science group.
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12. Low Mass CBC S5/VSR1
Surviving coincident triggers
Need to estimate false alarm rate of surviving triggers
estimate rate of accidental coincidence by performing “time-slide” experiments:
Introduce unphysical relative time shifts btw detectors before applying the coincident stage of the pipeline.
Interesting candidate events (or loudest ones) are submitted to a detection checklist procedure.
Perform software injections of simulated GW signals to evaluate the pipeline efficiency
If no detection, calculate upper limits on event rates
4 interferometers = 4 data sets
For each ifo: generate a template bank 2PN to cover the search mass range
Example for « Low Mass » search
(2-35 Msun)
Match filtering: keep triggers above a threshold
Signal To Noise Ratio
threshold
Require coincidence between interferometers
(in mass and in time)
→ Reduce background of accidental coincidences
Apply vetoes:
- Instrumental vetoes (poor data quality times)
Signal based vetoes (ex: ² test): check for consistency between signal in the data and detected waveform
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Low Mass CBC S5/VSR1
Targetted sources
Neutron Star - Neutron Star (BNS)
Neutron Star - Black Hole (NSBH)
Black Hole - Black Hole (BHBH)
Mass range
2-35 Moin total mass, with component mass from 1 to 34 Mo for LIGO
2-3 Mo in total mass of equal mass binaries for Virgo
Low frequency cutoff
40 Hz for LIGO IFOs
60 Hz for Virgo
Inspiral horizon distance:
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Low Mass CBC S5/VSR1
The integration of Virgo in the pipeline augmented the possible combinations of IFOs in coincident Science Mode
A new detection ranking statistic was applied to take into considerations the different noise background in the different mass regions and the different efficiency in detecting GW of certain IFOs combinations wrt others
One of the important result of this work is in fact the integration of Virgo in the pipeline, which is ready to be used on S6/VSR2 data
No GW were identified.
90% confidence UL combined with a prior S5 result were derived on the rate of coalescences:
( Mo)
( Mo)
( Mo)
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Low Mass CBC S5/VSR1
5.00 x 10-4
6.00 x 10-5
5.00 x 10-5
2.00 x 10-6
2.0 x 10-7
2.00 x 10-5
8.67 x 10-3
2.22 x 10-3
4.40 x 10-4
BNS
BHNS
BBH
Our UL
Optimistic estimate
Best estimate
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Low Mass CBC S5/VSR1
Software injections of simulated NS-BH and BH-BH spinning binaries were done to evaluate the efficiency of the search wrt spinning binaries signals
Our templates are for non-spinning binaries, hence the UL are slightly worser.
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17. Data Quality and Glitches
To study and remove bad quality data :
The Scientist on Schift have the duty to report any unusual ITF behavior (Logbook entry)
The online DQ monitors flag environmental instabilities
Offline KleineWeller-based vetoes are produced
Weekly Glitch shifts have been set up : loudest glitches are investigated individually
Example of a day with very good quality data :
Omega trigger rate ~ 0.5 Hz
SNR > 10 trigger rate ~ 2/hour
Most of high-SNR events are
DQ-flagged
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18. Data Quality and Glitches
DQ performances are evaluated on a week basis (updated twice a day) :
Against MBTA triggers :
Against Omega triggers :
For each DQ flag, is computed :
The dead-time
The use percentage
The efficiency
The SNR distribution plot
The SNR vs. time plot
DQ safety is evaluated online :
So far, no unsafe DQ flag has been found
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19. Data Quality and Glitches
Glitch shifts have been set up : loudest glitches are investigated individually
Two main goals of the glitch shifts :
To check that the online DQ flags do their job
To investigate the source of the loudest glitches (to correct / flag them)
Main tool : Omega scan
At Cascina ~2 scans are run every hour on the loudest event of Omega and MBTA
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20. Data Quality and Glitches
Glitch investigation
~ 10% glitches have a clear explanation given by the scans (seismic, dust,...) :
Most of them are flagged online by a DQ.
~ 50% glitches show correlations with other channels:
Efforts are made to understand these correlations
KW-based vetoes should be able to flag some of these glitches
~ 40% glitches are still a mystery
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Conclusions
We presented two LSC/Virgo analysis on S5/VSR1 data with their astrophysical implications
Virgo work on DQ, vetoes is fundamental for assessing the sensitivity of the searches.
On-line DQ production is required for S6/VSR2 on-line analysis
S6/VSR2 on-line and off-line analysis are going-on as reported in the DA report for the STAC.
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November, 2009
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