1 G Z Goals and status of the burst searches Antony Searle LIGO Lab, Caltech November 2008

2 Outline Scientific motivation Science goals Data in hand Recent results Status of S5 analyses Plans for S6 analyses G Z

3 Gravitational wave bursts Short-lived signals, lasting only a few cycles within the frequency band of the instruments »Typically from few milliseconds to few seconds and with 100-few kHz frequency content »Unknown or poorly known waveforms Sources »Core-collapse supernova »Merger phase of binary compact objects »Neutron star instabilities »Cosmic string cusps and kinks »The unexpected! Need to make minimal assumptions about the candidate signal G Z Dimmelmeier et al., astro-ph/

4 Burst search goals Direct detection of gravitational wave bursts from astrophysical sources Set upper limits on the rate and energy of gravitational wave bursts “Eyes wide open” or “untriggered” searches »Minimal assumptions about their waveform details »Search the whole sky and all times with collected data “Directed” or “triggered” searches guided by astronomical observations in the electromagnetic spectrum »Search around the directions and approximate times of Gamma-Ray Bursts (GRBs) and Soft Gamma Repeaters (SGRs) Low-latency analysis of data to: »To provide detector characterization input »To allow electromagnetic follow-ups of candidates G Z

5 What data do we have in hand? LIGO-GEO (LSC) Fifth Science Run (S5) »Nov 4, 2005 – Oct 1, 2007 »>365 days of 3-instrument coincidences »>400 days of 2-site coincidences Virgo Science Run 1 (VSR1) »May 18, 2007 – Oct 1, 2007 »>75 days of 3-site coincidences »>95 days of 2-site coincidences LSC-Virgo started data-sharing on May 18, 2007 »All data collected by the instruments after that day are being analyzed jointly Instruments at or close to their design sensitivities G Z

6 Instrument sensitivities Traditional burst searches High frequency searches

7 G Z Burst group publications in 2008 Search for Gravitational Waves Associated with 39 Gamma-Ray Bursts Using data from the Second, Third, and Fourth LIGO Runs Phys. Rev. D 77 (2008) Phys. Rev. D 77 (2008) A Joint Search for Gravitational Wave Bursts with AURIGA and LIGO Class. Quantum Grav. 25 (2008) Class. Quantum Grav. 25 (2008) »S3; first transient joint search with a bar detector First joint search for gravitational-wave bursts in LIGO and GEO600 data (to appear in CQG) arXiv: arXiv: »S4; first three-site coherent network analysis Implications for the Origin of GRB from LIGO Observations Astrophys. J. 681 (2008) 1419 (jointly with Inspiral group) Astrophys. J. 681 (2008) 1419 »S5; confidently excluded an inspiral in M31 (Andromeda) as the source Search for Gravitational Wave Bursts from Soft Gamma Repeaters (to appear in PRL) arXiv: arXiv: »S5 externally triggered search; constrained some SGR models

8 Burst searches in a nutshell Is the multi-interferometer response consistent with a plane gravitational wave? »For two sites: »Times of arrival must be less than light travel times between different sites »Frequencies (or other basis parameters) must be consistent (coincident analysis) »For three or more sites: »Times of arrival must determine a physical direction »Phases and amplitudes must be consistent with instrument responses for that direction (coherent analysis) What is the background? »Time-shift the data so these properties of gravitational waves are violated, producing O(100) signal-free datasets to assess the significance of an observation in the unshifted “zero lag” data What is the sensitivity? »Add a variety of simulated signals into the time-shifted datasets and measure the efficiency with which they are recovered G Z

9 Main burst searches on S5/VSR1 Untriggered all-sky all time »“Low” frequency ( Hz) »“High” frequency ( Hz) Electromagnetically triggered »Gamma-Ray Bursts »Soft Gamma Repeaters Broken into two epochs »S5 Year 1 »S5 Year 2 / VSR2 Most are nearing completion GEO is used as a follow-up instrument Multi-methods approach »Including coherent network techniques G Z

10 G Z S5 data quality and vetoes From Q-pipeline: excess w/r/t gaussian of unclustered triggers with SNR>5 A random H1 day, no data quality flags applied preliminary Extensive data quality and event-by-event veto studies based on ~300 auxiliary channels yielded significant veto flags that were used in a hierarchical way in the detection and upper-limit setting steps of the searches

11 All-sky search in S5-year1 f<200 Hz f>200 Hz red dots – zero lag triggers black dots – time shifted triggers No events above threshold No events above threshold Correlated SNR Chosen thresholds Searched for un-modeled bursts in the Hz frequency regime Three methods were involved (BlockNormal, coherent-WaveBurst and Q- pipeline) based on incoherent, coherent and hierarchical approaches to data analyses No signal consistent with a gravitational wave burst found Correlated SNR

12 G Z All-sky search in S5 Year 1 Analysis complete, paper is being drafted Paper to be presented to the collaboration at the December 2008 meeting and submitted for publication shortly after »A factor of 2 improvement in sensitivity with respect to S4 (2 x 10 –8 M  at 10 kpc or 0.05 M  emitted at Virgo Cluster), a factor of 10 in upper limit Detection Probability

13 S5 Year 2 / VSR1 all-sky search Extends methodology established in the corresponding S5 Year 1 search Incoherent (coincidence-based), fully coherent and hierarchical methods are being applied to joint data Virgo can make significant contributions in the search above 300Hz where its sensitivity becomes comparable to LIGO’s May contain an artificial signal added blindly to the instruments using the hardware injection system Nearing completion Similar “high” frequency searches in the kHz band G Z

14 Searches triggered by GRBs 213 GRB triggers from satellites during S5 run Known direction and approximately known time allows us to compare on-source and off-source correlations between the sites S5Y1 consistent with background; upper limits set »Excluded a merger in Andromeda as the source of GRB S5Y2/VSR1 underway with Virgo and the more advanced coherent methods it permits G Z

15 Other S5 and pre-S6 activities Astrophysically and cosmologically motivated searches »Targeting point sources, e.g., galactic center »Bursts from cosmic strings »Specialized searches for binary black holes, core-collapse supernovae Searches in varying stage of maturity and probability for completion in the next 12 months An “Astrowatch” run currently collects data with the 2-km LIGO Hanford detector and GEO; an insurance policy for a nearby supernova »Data being analyzed primarily for detector monitoring and characterization purposes as close to real time as possible »More in-depth analysis expected to take place for significant events reported by electromagnetic (or particle) observations »Test-bed for real-time analyses expected to start with S6 G Z

16 G Z Goals and plans for S6 LIGO and Virgo are currently undergoing upgrades that will provide a x2 sensitivity improvement in ~mid-2009 at which time S6 and VSR2 will commence Main S5 searches are expected to remain the group’s priority in S6 »Three-site network lets us continue to expand the use of coherent analysis Emphasis in setting up infrastructure and defining protocol for low latency burst searches in S6 and VSR2 »Hours-to-minutes scale latency targeted

17 Low latency searches in S6 Do everything faster and more automatically »Generate calibrated data with low latency »Generate triggers with low latency at LIGO and Virgo sites »Transfer triggers and/or data from LIGO and Virgo sites to a central location with low latency Make a useful product for followup with ground and space-based telescopes »Accurately (~1 degree) reconstruct direction, at detection threshold SNR, with low latency –Position Reconstruction group very active »Associate triggers with nearby galaxies »Provide error regions to “tile” with instrument FOVs »Control false rate to make good use of limited followup “slots” Make a useful product for detector characterization »Low-latency feedback to operators and for commissioning G Z

18 LIGO Lab’s role in bursts (Sep 2007-Aug 2008) Group Leadership (Katsavounidis, co-chair, with Shawhan (Maryland) & Hello (Orsay)) Review Committees Membership (O’Reilly, Robertson, Cannon, Blackburn, Zweizig, Chatterji) Participation in Science (Blackburn, Brunet, Cannon, Chatterji, Garofoli, Hoak, Hughey, Katsavounidis, Markowitz, O’Reilly, Raab, Robertson, Searle, Shi, Stein, Stuver, Torres, Whitcomb, Yakushin, Zweizig) »all-sky searches for unmodeled bursts, »externally triggered searches, »astrophysically and cosmologically motivated searches, »detector characterization, data quality and veto investigations, »algorithmic development for hierarchical and fully-coherent searches, »LSC-Virgo joint analysis activities. Calibration Team Membership (O’Reilly, Hughey)

19 Conclusions Burst searches of the LIGO, GEO and Virgo data from the S5/VSR1 runs are well underway »Flagship searches are expected to complete within the next 6 months We are preparing for S6/VSR2 »Enhanced detectors at three sites will greatly increase the science we can do »Low-latency external triggers a challenge and a priority LIGO Laboratory personnel contribute to all strands and lead many of them G Z