1. Swift ‘sub-prime’ GRB search Concept and motivation Implementation Goal is to bring proposal to LSC-V in March R Frey U Maryland LSC-V 18 Dec 2008 G080655-00-Z 1 LSC (so far): E. Harstad**, R. Frey, I. Leonor (U of Oregon) Swift BAT: J.R. Cummings, H.A. Krimm (NASA GSFC), D.M. Palmer (LANL)

2. Swift BAT FOV: 1.4 sr In general, a significant rate increase plus an image (position)  “a burst”, GCN notice, slew Two classes of “sub” GRBs : 1.Real sources just outside the FOV (“rate trigger”) 2.Real sources with rate below the usual threshold (“sub threshold”) We are interested in both. R Frey U Maryland LSC-V 18 Dec 2008 G080655-00-Z 2

3. BAT trigger rate and threshold R Frey U Maryland LSC-V 18 Dec 2008 G080655-00-Z 3 Swift internal only Trigger rate (au) Burst significance Swift’s goal is primarily to report GRBs with very high purity There are clearly good GRBs below the usual BAT threshold

4. GRB and GW brightness GRBs which are dim in gamma-rays are not necessarily correlated with low GW brightness e.g. short GRBs are dimmer than long (even though nearer); but are much stronger in GW luminosity gamma-rays from GRBs are beamed: position of Swift in beam is significant effect R Frey U Maryland LSC-V 18 Dec 2008 G080655-00-Z 4

5. Analysis outline The rate triggers (outside FOV): many of these already show up in the GCN circulars as GRBs after being confirmed by IPN, et al  High purity; not a large number of triggers  No position – analyze using time-coincidence analysis The sub-threshold triggers:  Stay close to nominal Swift GRB threshold  The trigger information must be disentangled from several BAT log files and data products (in progress: Emelie)  Analyze as for main S5 GRB pipeline This is a “standard” ExtTrig style search Use reviewed pipelines Omega pipeline is good candidate for bursts pipeline. CBC ? Current plan involves only S5 R Frey U Maryland LSC-V 18 Dec 2008 G080655-00-Z 5

6. Next steps The Swift data is already public, including logs files, debug streams, etc. No permissions needed.  Some special knowledge is required to interpret it. But the BAT folks have been very helpful. The BAT crew simply informs the Swift PI that this activity is taking place and that they are to be co- authors on any resulting publications. Only impact on LSC resources is the analysis review. We would like to propose this to the LSC-V for the Spring LVC meeting R Frey U Maryland LSC-V 18 Dec 2008 G080655-00-Z 6