The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey -- I. Survey design and processing pipeline

Abstract

We present an overview of the Southern-sky MWA Rapid Two-metre (SMART) pulsar survey that exploits the Murchison Widefield Array's large field of view and voltage capture system to survey the sky south of 30 • in declination for pulsars and fast transients in the 140-170 MHz band. The survey is enabled by the advent of the Phase II MWA's compact configuration, which offers an enormous efficiency in beam-forming and processing costs, thereby making an all-sky survey of this magnitude tractable with the MWA. Even with the long dwell times employed for the survey (4800 s), data collection can be completed in <100 hours of telescope time, while still retaining the ability to reach a limiting sensitivity of ∼2-3 mJy (at 150 MHz, near zenith), which is effectively 3-5 times deeper than the previous-generation low-frequency southern-sky pulsar survey, completed in the 1990s. Each observation is processed to generate ∼5000-8000 tied-array beams that tessellate the full ∼610 deg 2 field of view (at 155 MHz), which are then processed to search for pulsars. The voltage-capture recording of the survey also allows a multitude of post hoc processing options including the reprocessing of data for higher time resolution and even exploring image-based techniques for pulsar candidate identification. Due to the substantial computational cost in pulsar searches at low frequencies, the survey data processing is undertaken in multiple passes: in the first pass, a shallow survey is performed, where 10 minutes of each observation is processed, reaching about one-third of the full search sensitivity. Here we present the system overview including details of ongoing processing and initial results. Further details including first pulsar discoveries and a census of low-frequency detections are presented in a companion paper. Future plans include deeper searches to reach the full sensitivity and acceleration searches to target binary and millisecond pulsars. Our simulation analysis forecasts ∼300 new pulsars upon the completion of full processing. The SMART survey will also generate a complete digital record of the low-frequency sky, which will serve as a valuable reference for future pulsar searches planned with the low-frequency Square Kilometre Array.

Reduced-resolution beamforming: Lowering the computational cost for pulsar and technosignature surveys

“…SMART (Bhat et al 2023a) is a pulsar and fast transient search project on the MWA, using the 128-tile compact configuration (Wayth et al 2018). SMART aims to conduct a pulsar search across the full sky below 30 • declination, to a limiting sensitivity (10σ ) of 2-3 mJy.…”

“…We extrapolate that the post-processing requirements on OzSTAR would drop from ∼14 000 to ∼636 kSU. The SMART team anticipates securing 500-600 kSU per annum (Bhat et al 2023a), meaning it is plausible that the entire survey could be processed within a year if reduced-resolution beamforming is adopted (instead of an implausible 22 years).…”

“…Nevertheless, there are active pulsar searches on several radio array telescopes (e.g. Sanidas et al 2019;Chen et al 2021;Singh et al 2023;Bhat et al 2023a). fast radio burst (FRB) searches (e.g.…”

“…The LOTASS c survey used the dense central 'Superterp' core of LOFAR to balance field of view against sensitivity. Similarly, the Murchison Widefield Array (MWA) SMART d (Bhat et al 2023a) uses the 'compact' MWA configuration of 128 tiles within ∼800 m.…”

“…The LOTAAS survey searched across 10 120 DM trials, which required 30M CPU-core hours on the Cartesius supercomputer to process data up to January 2019 (Sanidas et al 2019). Based on first-pass benchmarks, the SMART survey will require ∼60M CPU-core hours to process ∼93 hours of observational data using the OzStar supercomputer (Bhat et al 2023a). As the SMART team anticipate receiving ∼0.5-0.6M CPU-core hours per semester, they are in the process of optimising and accelerating their search pipeline to ensure processing is possible.…”