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 deg2 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.

The Huge Magnetic Toroids in the Milky Way Halo

“…Finding more pulsars in the Galactic halo and measuring their RMs can help us to better figure out the local RM contributions, which is necessary for separating the halo and local contributions. This can be achieved in the future by the Square Kilometre Array or its pathfinders (see Han et al 2015) -for example, the Southern-sky MWA Rapid Twometre pulsar survey (Bhat et al 2023), the MeerTRAP survey for pulsars and fast transients with MeerKAT (Sanidas et al 2018), the LOFAR Tied-Array All-Sky Survey for radio pulsars and fast transients (Sanidas et al 2019), and also our FAST pulsar survey (Han et al 2021). A refined model for the Galactic distribution of electron density is also a key element for figuring out the nature of the magnetic field toroids.…”

Discovery and Follow-up of a Quasiperiodically Nulling and Subpulse Drifting Pulsar with the Murchison Widefield Array

“…The SMART survey is an all-sky pulsar search project that exploits low frequencies and the large field of view of the Murchison Widefield Array (MWA; Tingay et al 2013) to survey the southern sky for pulsars and transient signals (Bhat et al 2023a(Bhat et al , 2023b. It employs long dwell times (80 minutes per pointing) and records data in the form of raw voltages (rather than channelized detected data).…”

“…The survey uses the compact configuration (Wayth et al 2018) of the MWA, which has a tied-array beam size of ∼24′. The large field of view (∼600 deg 2 at 150 MHz) and the voltage recording means the entire southern sky can be surveyed in ∼100 hr (Bhat et al 2023a). However, the use of low frequencies also means a very large number of dispersion measure (DM) trials and, as a result, the processing generates millions of candidate signals which must then be scrutinized after filtering through machine-learning software.…”

“…It displays subpulse drifting behavior with a consistent drift rate and a singular drift mode. This pulsar was discovered in the first-pass processing of the Southern-sky MWA Rapid Two-meter (SMART) pulsar survey (Bhat et al 2023a(Bhat et al , 2023b. The discovery of the pulsar, initial follow-up, and the observations used are described in Sections 2.…”

The GMRT High Resolution Southern Sky Survey for Pulsars and Transients. VI. Discovery of Nulling, Localization, and Timing of PSR J1244–4708

“…There are many pulsar surveys trying to increase the pulsar population by using more sensitive telescopes and new search techniques (e.g., Bhattacharyya et al 2016;Keane et al 2018;Han et al 2021;Ridolfi et al 2022;Bhat et al 2023;Singh et al 2023). Along with normal and millisecond pulsars, many new exciting time-domain transients have been discovered by these surveys, including ultra-long-period pulsars (e.g., Caleb et al 2022), rotating radio transients (RRATs; e.g., McLaughlin et al 2006;Karako-Argaman et al 2015), and many new fast radio bursts (FRBs; e.g., Bhandari et al 2018;Bailes 2022).…”