Update TKP meeting Amsterdam June 2011 FRATS: Real-time triggering on Fast Radio Transients with LOFAR Sander ter Veen, Pim Schellart, Clancy James, Heino Falcke for the LOFAR Transients and Cosmic Ray KSP Radboud University Nijmegen 

29-06-11 2 If I may look tired... LIGHTNING! 

29-06-11 3 Science ● Real-time serendipity search for bright dispersed millisecond pulses – Pulsars (Giant pulses) – RRATS – Flare stars – Exoplanets 

29-06-11 4 Real-time detection principle Station beam Dipole/Tile data Dipole/Tile data Dipole/Tile data TBB buffers Station beam Dipole/Tile data Dipole/Tile data Dipole/Tile data TBB buffers Incoherent Or Coherent Beam Station beam Trigger algorithm Obtain data Obtain data 

29-06-11 5 Offline data analysis Station beam(s) Dipole/Tile data Dipole/Tile data Dipole/Tile data TBB buffers Station beam(s) Dipole/Tile data Dipole/Tile data Dipole/Tile data TBB buffers Many Coherent Beams (high time- resolution images) Station beam Search algorithm Accurate Position (down to few arcsec or less) 

29-06-11 6 Detection philosophy ● Commensal observation mode – Large sky/time coverage for rare events ● Offline data analysis similar to Cosmic Ray data analysis ● No detailed LOFAR follow up needed to determine position ● More accurate position helps Multi-WL ● Real-time: no extra processing time 

29-06-11 7 Trigger method 20 ms 195kHz ● 1 subband with 64 channels G iant Pulse from C rab pulsar DM=5, 190 MHz-150 MHz Δt = 0.36 s 190 Mhz-110 Mhz Δt = 1.12 s 

29-06-11 8 Trigger method 20 ms 195kHz 20 blocks ● 1 subband with 64 channels Correct for dispersed time Check for coincidence Require K out of N subbands G iant Pulse from C rab pulsar 

29-06-11 9 Trigger Method ● Take beamformed data in power ● Divide total bandwidth in several bands ● Dedisperse every band and look for a peak ● Peak: Power > N * std + mean ● Check for coincidences between the bands 

29-06-11 10 Status: principle proven ● Crab Giant pulse Trigger Re-detection 

29-06-11 11 Status: principle proven ● Crab Giant pulse Trigger Precise localisation 

29-06-11 12 TBB trigger ● “External” trigger via ssh ● Last year shell scripts ● This year python library ● PyQt GUI ● Next few months: MAC/SAS implementation ● UDP trigger protocol 

29-06-11 13 Large scale test ● LOFAR Pulsar Pilot Survey (dec 2010) ● 7 incoherent beams, 6.8 Mhz, 8 divisions ● 255 pointings taken so far ● Real-time triggering on part of the pointings ● Off-line analysis on other pointings ● No TBB data dumps ● 30 DM trials between [10,25] 

29-06-11 14 The good news ● Found 7 pulses from pulsar B0834+06 

29-06-11 15 The bad news ● Many false triggers obs21756 (R) obs21781 obs21783 obs21786 obs21757 obs21796 0 50 100 150 200 250 triggers 

29-06-11 16 Check: DM=0 signal? obs21756 (R) obs21781 obs21783 obs21786 obs21757 obs21796 0 50 100 150 200 250 triggers no RFI within 50 samples no RFI within 100 samples no RFI within 500 samples 

29-06-11 17 Check: Multiple beam trigger? obs21756 (R) obs21781 obs21783 obs21786 obs21757 obs21796 0 50 100 150 200 250 triggers no 3 beam within 50 samples no 3 beam within 100 samples no 3 beam within 500 samples 

29-06-11 18 Check: Combine both? obs21756 (R) obs21781 obs21783 obs21786 obs21757 obs21796 0 50 100 150 200 250 triggers within 50 samples within 100 samples within 500 samples 

29-06-11 19 RFI excision ● DM=0 with multi-beam check is efficient but not yet perfect ● Need to check data after trigger (step / long duration RFI ) 

29-06-11 20 Observing plans ● MSSS: commensal incoherent beam ● LOTAS: add additional stations – (19 Coherent beams pulsar survey) ● Needs option to select certain stations for beamforming ● All-sky low DM LBA survey 

29-06-11 21 All sky Low DM LBA ● Low DM: Distinguishable at low freq ● LBA: Wide beam, fast survey ● All -sky: arc of beams in declination ● Scan one RA ● Move to next RA ● Pointing duration depends on bandwidth ● New beam center at FWHM 

29-06-11 22 Observation parameters ● More bandwidth by more 24hr runs or less beam overlap Freq (MHz) Nr Dec Bandwidth (MHz) Repointing time Integration time Max DM (1.3 s) 10 6 8 55 52 0.02 20 12 4 27 24 0.3 30 18 2.7 18 15 1.6 40 24 2 14 11 5 50 29 1.7 11 8 11.5 60 35 1.4 9 6 24.2 70 42 1.2 8 5 44.7 80 47 1.0 7 4 80.2 

29-06-11 23 Summary ● Principle proven: FRATS works! ● Need to develop RFI discrimination ● Optimize search algorithm (more DMs) ● Test / run LBA survey and commensal to other data ● Test / develop further TBB identification