Pulsar searches and timing with the SKA

The Square Kilometre Array (SKA) is a planned multi purpose radio telescope with a collecting area approaching 1 million square metres. One of the key science objectives of the SKA is to provide exquisite strongfield tests of gravitational physics by finding and timing pulsars in extreme binary systems such as a pulsar-black hole binary. To find out how three preliminary SKA configurations will affect a pulsar survey, we have simulated SKA pulsar surveys for each configuration. For surveys along the Galactic plane, which we define to be |l| < 45◦ and |b| < 5◦, the optimal centre frequency lies just above 1GHz. For the rest of the sky, a lower frequency of around 600MHz will maximise the survey yield, although special areas like the Galactic Centre may need frequencies of 10 GHz or more. We describe a simple strategy for follow-up timing observations and find that timing such a sample of pulsars could be achieved in 1–6 days, depending on the configuration. This time estimate does not include observing time for high precision timing which is required for the Key Science Project and is significantly larger, depending on whether aperture arrays are available. We also study the computational requirements for beam forming and data analysis for a pulsar survey. Beam forming of the single-pixel feed 15-m dishes using the 1-km core of the SKA requires about 2.2×10 ops. This number can be reduced when the dishes are placed in sub-arrays. When the 15-m dishes are equipped with phased array feeds, the field of view can be increased by over a factor of 30. The required computational power then scales linearly with the field of view. For the aperture array, the required computational power for beam forming is 1.4×10 ops for the 1-km core. The corresponding data rate from a pulsar survey using such a core is about 4.7×10 and 1.6×10 bytes per second for the dishes and the aperture array, respectively. The required computational power for a deep real time analysis is estimated to be 1.2×10 and 4.0×10 ops for the dishes and the aperture array, respectively. We estimate that the total number of pulsars the SKA will detect with the initially available computing power is around 15 000, when using the 1-km core and 30 minutes integration time, compared to 30 000 pulsars that are potentially detectable.