Overview

1. Real-time search for gravitational wave transients during S6/VSR2:Principles, thoughts and plansErik KatsavounidisMITfor the LSC-Virgo Burst groupTelecon, June 25, 2008

2. Overview • Implement a search for gravitational wave transient with <30minutes latency • Strong and broad arguments for such target: • Compelling science from real-time follow-up of outgoing/incoming triggers • Unique exercise for future running of the instruments • Address detector characterization aspects and expedite closure of offline analyses • Provide event stream for Target-of-Opportunity telescope time and peer-to-peer external collaborations • Not intending to declare detection outside the LSC-Virgo in real-time (or in a short or expedited way), at least within the S6/VSR2 time-scale • Implement a hierarchical search pipeline • Have basic implementation ready for early engineering runs, assumed to come to life in ~December 2008 and be ready for S6/VSR2 in ~Spring 2009 • Identify core team from within the burst group that will work with Inspiral, Detector Characterization and DASWG groups in the implementation and carrying out of the search

3. Today’s telecon goals • Agree on principles • Turn-around time of the online search • Top-level structure of the search • Uniformity (or not!) of implementation across detector sites • Identify areas to which the design and implementation of the search should be broken down • Identify lead and team members • Rough timeline

4. Motivation • Rapid and systematic evaluation and cataloguing of data quality pertinent (and not) to burst searches • Built as much as possible of the offline analyses on data products of the online search  expedite “closure” of offline analyses • Prompt identification and (internal) follow-up of detection candidates; time-critical detector-specific investigations • Prompt E/M follow up of gravitational wave events • Capture the earliest possible light associated with astrophysical gravitational wave burst sources • Multi-band astronomy the ultimate goal • Increase detection confidence/make a case of otherwise marginal detection • Prompt GW follow up of E/M events • Reach out astronomical community with astrophysically interesting non-detection statements in a matter of weeks (and not months)

5. Doable? • S5 punch line: Equinox event, GRB070201 had available data in matter of hours • How to turn this down by an order of magnitude (or two)! ?

6. Implementation principles • Need a group-wide project definition and participation • Need to work with Inspiral, Detector Characterization and DASWG (other?) groups for a common solution that meets our science goals, cross-groups compatible data products, information and action plan • Should be realistic given the time-scale and available human resources within the group and the wider collaborations

7. Punch line implementation goal • Establish within 30 minutes the statistical significance of coincidence events recorded by the instruments reflecting our best understanding of the instruments (i.e., fold as much of DQ/vetoes as possible) and threshold on it • Provide timing/directional information on such events to telescopes for electromagnetic follow-ups either through peer-to-peer agreements or Target-of-Opportunity observations • If process is triggered by a significant external trigger turn online analysis to a prompt (~weeks) science result

8. Implementation details • General scheme of the search is hierarchical starting with trigger generation on a single-instrument basis that is followed up coherently – external triggers are directly analyzed coherently • Per-instrument basis: • Segment definition: O(1) minute delay • Calibrated data: O(1) minute delay • Event generation: O(1) minute delay • Auxiliary channel analysis: O(1) minute delay • Apply DQ/vetoes locally (and never propagate vetoed events?): O(5) minute delay • Hardware injections • Multi-interferometer basis: • Individual instrument segments, calibrated data and events available in a central location: O(5) minute delay • Perform time-frequency coincidence • Use timing/amplitude (and their errors) for source reconstruction • Fully coherent analysis • ExtTrig analysis • Likelihood sky maps, positioning of the source on differential luminosity density maps dL/dW (i.e., where is the luminous mass as a function of depth) dL/dW • Background estimation • Efficiency studies

9. Technical solutions • Lessons learnt from the S5/VSR1 technical solutions • What we know that will NOT work out for us • Preferred solutions

10. Online search working groups • Organize work in small groups within bursts • Scope out their mission, define some timeline and press ahead • Tentative working groups: • DASWG liaisons • Computing solutions • ExtTrig solutions • Signal injections • Data quality and vetoes • Search pipeline • Communication protocol • The Search Czars

11. Timeline/to-do list • Agree today/by end of this week on principles • Turn-around time of the online search • Top-level structure of the search • Uniformity (or not!) of implementation across detector sites • Identify today/next week working group membership • Present planning document to collaborating groups (DASWG, inspiral, DetChar) and to collaborations leadership (1-2 weeks?) • Physics-related key investigations (1-2 months) • Establish level of calibration accuracy needed to achieve certain level of pointing accuracy, null stream veto efficiency • Establish pointing accuracy using timing/amplitude and using real data+MDCs already in hand • Implementation-related key investigations (2-3 months) • Be ready with a basic solution for a December 2008 Engineeering run