| Description: | LOTAAS is the LOFAR Tied-Array All-Sky Survey, an ongoing LOFAR all-northern-sky survey for pulsars and fast transients - i.e. anything that emits millisecond timescale dispersed bursts. Using only the Superterp HBA stations, each pointing is comprised of three sub-array pointings and within the field of view of each incoherent beam we also form 61 tied-array beams. We also generate an additional 12 tied-array beams to point at known sources giving a total sum of 222 beams per survey pointing. In other words, this is a pulsar and fast transient survey approach unlike any other and a unique stepping stone on the path to surveying with SKA-Low. With a bandwidth of 32 MHz, a spectral resolution of 12 kHz, and a sampling time of 492 microsec, LOTAAS generates data at an astounding rate of 35 Gbps (close to the total possible system throughput of the LOFAR CEP2 network). Each 1-hour pointing produces 16 TB of raw data.
LOTAAS has been observing since December 2012, and we have processed 160 pointings on the Dutch supercomputer Cartesius (operated by SURFsara). Using Fourier-based pulsar searching methods we have produced more than 3 million pulsar candidates. A machine learning classifier is then applied to the candidates and the most promising go forward for human inspection. LOTAAS has so far discovered 8 new pulsars. These are marked with large red stars in the above figure, which also shows the current observed sky coverage in green. Along with LOFAR's first two pulsar discoveries in the commissioning survey LOTAS, which are marked with orange stars above (Coenen et al. 2014), LOFAR now has a total of 10 pulsar discoveries. The LOTAAS survey has also redetected 80 known pulsars including 4 independent discoveries of pulsars originally discovered by the Green Bank North Celestial Cap Survey. The survey is only one third of the way through its first pass (of three) of the sky, with many more pulsars waiting to be discovered. We are also sifting through the already processed data to find intermittent pulsars, and single dispersed bursts. |
