“Data quality studies for burst analysis of Virgo data acquired during Weekly Science Runs “

1. “Data quality studies for burst analysis of Virgo data acquired during Weekly Science Runs “ E.Cuoco, EGO on behalf of Virgo Collaboration E. Cuoco, on behalf of Virgo collaboration

2. WSR goals • To ease the transition between commissioning to data taking • 2.5 days during week-end, roughly one per month • Provide data sets taken in stationary condition for : • Commissioning studies • Search analysis (online, offline and noise studies) • WSR1 08/09-11/09 2006 : duty cycle 87.7% • WSR2 22/09-25/09 2006 : duty cycle  71.2% • WSR3 06/10-09/10 2006 (failed) • WSR4 13/10-16/10 2006 (failed) • WSR5 10/11-13/11 2006 : duty cycle 64.2% • WSR6 01/12-04/12 2006 : duty cycle 80.5% • best sensitivity reached (4 Mpc NS-NS horizon for an optimally oriented source, SNR=8) E. Cuoco, on behalf of Virgo collaboration

3. Goal of this study • Study the “quality” of the Virgo data • Detect all kinds of glitches in the data which may spoil a burst search (loudest events study) • Understand the origin of these glitches, when possible … • Study the stationarity of the burst trigger rate • Study possible vetoes strategy to suppress loud triggers • Set up “tools” and provide information for the burst searches (DataQuality flags and vetoes) E. Cuoco, on behalf of Virgo collaboration

4. DataQuality & Vetoes • DQ flags: list of periods during which the ITF is badly functioning (photodiodes saturation, no calibration, noisy Second Stage Frequency Stabilization loop (SSFS), DAQ problem…). • These periods can last from 1 second up to several hours. • They are applied a priori or a posteriori on the triggers list produced by a burst pipeline. • For the moment they concern only “obvious” problems but may concern in the future environmental condition (weather, …) if useful for the burst search • Vetoes: list of short periods during which a fake burst signal could be visible in the Dark Fringe channel due to any cause except a genuine GW. • They are applied on triggers’ lists. E. Cuoco, on behalf of Virgo collaboration

5. Virgo burst pipelines Excess of Mean Estimation on different window size Wavelet Transform Coefficient threshold Energy estimation Wiener filtering with gaussian peak templates Wiener filtering with exponential gaussian templates • Time domain • Mean Filter (MF) Time-Frequency map with different window Work on whitened data • Time -Frequency • Power Filter (PF) • Wavelet Detection Filter (WDF) • Correlator • Peak Correlator (PC) • Exponential Gaussian Correlator (EGC) E. Cuoco, on behalf of Virgo collaboration

6. Data Quality flags study • Few problems identified so far: • Dark fringe outport photodiodes saturation • NE/WE/BS/PR mirror coil driver saturation • Second Stage Frequency Stabilization (SSFS) correction saturation • SSFS electronics problem • Timing problems (DAQ) (WSR5) • Photodiode shutter opening (WSR2) • Data quality segments given by the h reconstruction processing • White noise injection segments • Bad quality when the lines are not high enough • It has been checked that all these problems create loud events in the dark fringe • Definition of Data Quality segments to flag these periods • Most of these flags can be applied a posteriori on trigger lists E. Cuoco, on behalf of Virgo collaboration

7. DQ segments application on MF triggers: WSR1 WSR1 photodiode saturation SSFS saturation E. Cuoco, on behalf of Virgo collaboration

8. DQ segments application on MF triggers:WSR5 WSR5 SSFS saturation timing E. Cuoco, on behalf of Virgo collaboration

9. DQ segments application on MF triggers:WSR6 WSR6 Coil drivers saturation The loudest events are suppressed by using these DQ flags E. Cuoco, on behalf of Virgo collaboration

10. Loudest glitches study We found only a few categories in WSR data: • Oscillations in control loops (longitudinal and angular dof): “z” events (low frequency events <100 Hz) • Noise increase on the full bandwidth due to laser frequency noise coupling temporary increase (duration <few seconds): that generates some “Burst of Burst” events (“BOB” events) In C6/C7 data set, the origin of the laser frequency noise coupling increase has been identified to be due to the residual angular motions of the mirrors which were too loose • SSFS electronics saturation events • Study of environmental channels (seismometers, magnetometers, acoustic probes …) We did not find so far any loud glitches in the dark fringe due to environmental noise … E. Cuoco, on behalf of Virgo collaboration

11. Events in the control signals E. Cuoco, on behalf of Virgo collaboration

12. Example of a BOB event • long duration events (up to few seconds), • large frequency band content • due to a coupling of the laser frequency noise and angular motion of the mirror E. Cuoco, on behalf of Virgo collaboration

13. Example of a problem with the SSFS 2 seconds 2 seconds Dark fringe Exclude 1 second before and 1 second after the event in the SSFS channel E. Cuoco, on behalf of Virgo collaboration

14. Veto for the SSFS saturation events WDF SNR of the triggers obtained on the channel which “monitors” the SSFS E. Cuoco, on behalf of Virgo collaboration

15. SSFS channel as Veto SNR>85, Dt=0.1 More details in M.Delprete poster E. Cuoco, on behalf of Virgo collaboration

16. Looking at the signal used to control the Power Recycling cavity length z-events Snr>30 ,Dt=0.1 E. Cuoco, on behalf of Virgo collaboration

17. WSR5:Dark fringe WDF events distribution E. Cuoco, on behalf of Virgo collaboration

18. WSR5: Cleaning the Dark fringe For SSFS SNR >85 Dt=0.1 For z-events, SNR>30 Dt=0.1 E. Cuoco, on behalf of Virgo collaboration

19. Enviromental channels: Magnetometers in North End tower • Glitches every 3-4secs E. Cuoco, on behalf of Virgo collaboration

20. Glitches inWE-NE magnetometers E. Cuoco, on behalf of Virgo collaboration

21. Lightning? Dark fringe E. Cuoco, on behalf of Virgo collaboration

22. Coalescing binaries horizon and seismic noise WSR1 WSR6 Horizon fits quite well an empirical formula: 2.7 (4.3) Mpc – (wind+sea). “wind” is the North End tower top stage motion in the region 30-100 mHz, “sea” is the motion in the region 100 mHz-1 Hz E. Cuoco, on behalf of Virgo collaboration

23. Burst trigger rate and weather condition ? • Study of the burst trigger rate as function of time (rate averaged on 10 minutes) • Horizon seems to follow the low frequency (<1Hz) seismic activity seen by the top of the suspensions • Comparison with the Common Mode Rejection Ratio which gives the coupling between the laser frequency noise and the dark fringe E. Cuoco, on behalf of Virgo collaboration

24. Burst trigger rate and weather condition: WSR1 • The trigger rate follows • the seismic noise <1Hz • The trigger rate follows the • evolution of the CMRR E. Cuoco, on behalf of Virgo collaboration

25. Burst trigger rate and weather condition: WSR5 E. Cuoco, on behalf of Virgo collaboration

26. Burst trigger rate and weather condition: WSR6 • The trigger rate follows • the seismic noise (<1Hz) • The trigger rate does not • follows the evolution of • the CMRR E. Cuoco, on behalf of Virgo collaboration

27. Conclusions • WSR data sets have been analyzed offline using glitches finders algorithms to provide useful information for the burst searches • Identification of all problems generating huge glitches  DataQuality flags defined to suppress a posteriori these periods • Identification of the loudest remaining glitches. A few categories have been identified • Setup of veto strategy for the identified sources of glitches • We found correlation between the transient trigger rate and the weather condition E. Cuoco, on behalf of Virgo collaboration

28. Spare slides E. Cuoco, on behalf of Virgo collaboration

29. Horizon vs weather condition Seismic noise: quite quiet during the week-end! E. Cuoco, on behalf of Virgo collaboration

30. A bob event Dark fringe (whiten) Time (s) Frequency (Hz) E. Cuoco, on behalf of Virgo collaboration

31. BOB mechanism Proposed Mechanism • at high frequency, frequency noise dominates • Pr_B1_ACp = a * dna related to Common Mode Rejection Ratio a varies with time by a significant amount (up to a factor 10) a variations are mainly driven by angles E. Cuoco, on behalf of Virgo collaboration

32. Dark fringe noise increase as function as the North End mirror θy angle -2 -1 0 1 2 x 10-8 1.6 1.5 1.4 1.3 1.2 Pr_B1_ACp RMS 1.1 1. 0.9 0.8 0.7 NE_ty C7 E. Cuoco, on behalf of Virgo collaboration