at lower frequencies arrive later. • Data is split in small channels (~ kHz ) • Channels are summed according to dispersion law • Many (>100) DM trials Lorimer et al. 2007 Trigger moment Stop delay
element Data stored, stopped, dumped to disk. Reproduce any LOFAR signal; Also your data! Limited memory => limited time Beamsize: LBA: All-sky (30000 sq. degr) HBA: 500 sq. degr. 9
Dedispersion in multiple frequency bands Coincidence requirement between the bands Image from TBB data Use to identify source +Multiwavelength Follow-up 4 stations See Presentation by Emilio at 17:05
trial vs DM pulse • Decreases efficiency • Compared samples summed for for one DM trial compared to the next • 150-200 DM trials in real-time • ΔDM=0.1 reasonable • Lower frequencies problematic, skip? • Time window 200 ms
trials real-time • Trigger parameters defined • First test observations have been run (3x 4 hours) - Handled triggers were all RFI events, apart from a trigger on B1919+21 • To do: - Run during remaining MSSS LBA observation (100 h) - Run during MSSS HBA observations (full sky) - Run during other observations? - Make FRATS an easy add-on in LOFAR online system - Further tuning of trigger algorithm - Only use core-stations for incoherent beam • TBB localisation (see talk by Emilio Enriquez) • Trigger from ARTEMIS and other sources 29
with a wide FoV parallel to other observations. Transient Buffer Boards see the whole sky for 1.3 seconds and thereby are a powerful tool to identify short duration signals First commissioning observations have been run 30