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NAM2012 - All Presentation Details

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Radio Detection of Cosmic Particles and Fast Radio Transients with LOFAR

Author: Heino Falcke

Radboud Univ. Nijmegem/ASTRON/MPIfR Bonn

Co-Authors: LOFAR Cosmic Ray and Transients Key Science Projects

Session: INS4: LOFAR, the LOw Frequency ARray: Ongoing Developments and Early Results

Presentation type: Talk      10:41  Thursday 29th 10:00-11:15 

Summary:

The digital nature and large field of view of LOFAR makes innovative searches for fast radio flashes of astrophysical origin possible. As a first stepping-stone in this direction LOFAR has begun to regularly observe high-energy cosmic rays. Once a cosmic ray hits the Earth atmosphere, a shower of secondary particles is created, rushes though the geomagnetic field, and produces a bright radio flash for some tens of nanoseconds. The LOPES (LOFAR Prototype Station) experiment already detected this emission and showed that radio is a good tracer of particle energy. Models of the emission suggest that radio is also a potentially good tracer of particle composition. As a consequence, the new LOFAR radio telescope has UHECRs detection built in: All ~2500 individual antenna elements in LOFAR come with a memory ring buffer (Transient Buffer Board, TBB) and real-time pulse detections, allowing particles above 10^17 eV to be detected. Moreover, a small particle detector array, LORA (LOFAR-Radboud Airshower array), provides cross-calibration and external triggers when desired. Using first commissioning data, the radio emission of UHECRs has been detected with unprecedented detail. As a follow-up step the TBBs can also be used to search for sub-second astrophysical transients such as giant pulses from pulsars, stellar and planetary flares, cosmic ray impacts on the moon, and other exotic events. A trigger system has been developed and tested with giant pulses from pulsars, which can detect dispersed pulses and dump the buffer. Offline processing of TBB data can then reconstruct pulse direction and verify the extra-terrestrial origin of these pulses. This will open an entirely new parameter space for real-time detection of sub-second radio transients.

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