The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey—II. Survey status, pulsar census, and first pulsar discoveries

Abstract

In Paper I, we presented an overview of the Southern-sky MWA Rapid Two-metre (SMART) survey, including the survey design and search pipeline. While the combination of MWA’s large field-of-view and the voltage capture system brings a survey speed of ∼450 deg2 hr−1, the progression of the survey relies on the availability of compact configuration of the Phase II array. Over the past few years, by taking advantage of multiple windows of opportunity when the compact configuration was available, we have advanced the survey to 75% of the planned sky coverage. To date, about 10% of the data collected thus far have been processed for a first-pass search, where 10 min of observation is processed for dispersion measures out to 250pc cm−3, to realise a shallow survey that is largely sensitive to long-period pulsars. The ongoing analysis has led to two new pulsar discoveries, as well as an independent discovery and a rediscovery of a previously incorrectly characterised pulsar, all from ∼3% of the data for which candidate scrutiny is completed. In this sequel to Paper I, we describe the strategies for further detailed follow-up including improved sky localisation and convergence to timing solution, and illustrate them using example pulsar discoveries. The processing has also led to re-detection of 120 pulsars in the SMART observing band, bringing the total number of pulsars detected to date with the MWA to 180, and these are used to assess the search sensitivity of current processing pipelines. The planned second-pass (deep survey) processing is expected to yield a three-fold increase in sensitivity for long-period pulsars, and a substantial improvement to millisecond pulsars by adopting optimal de-dispersion plans. The SMART survey will complement the highly successful Parkes High Time Resolution Universe survey at 1.2–1.5 GHz, and inform future large survey efforts such as those planned with the low-frequency Square Kilometre Array (SKA-Low).

The Green Bank 820 MHz Pulsar Survey. I. Survey Overview and Initial Results

“…These surveys are chosen to cover a wide range of observing frequencies and sky positions to avoid biases from individual survey setups. The simulations here utilized the total number of pulsar/MSP detections from the following surveys, where we define an MSP as having a period 30 ms: GBNCC (670/70; McEwen et al 2020), AODrift (75/33;Martinez et al 2019), PALFA (207/46;Parent et al 2022), LOTAAS (300/ 11; Coenen et al 2014;Sanidas et al 2019), PMPS (916/28; Sengar et al 2023), PKS70 (298/17;Lyne et al 1998), and SMART (180/14;Bhat et al 2023). We supplied the total number of known pulsar detections from all of these surveys, N tot , and PsrPopPy generates pulsars until N tot is detected.…”

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).…”

“…We used a strategy similar to that used by Swainston et al (2021) and Bhat et al (2023b) for obtaining an initial localization of the pulsar using SMART data. This method exploits the fact that the MWA data are stored as raw voltages, thereby allowing us to beamform at multiple nearby positions (in the form of a dense grid) and compare the significance of the resultant detections with that expected from the predicted tied-array beam responses.…”

“…As described in Bhat et al (2023b), follow-up with sensitive high-resolution interferometers like the upgraded Giant Metrewave Radio Telescope (uGMRT) is an integral part of the follow-up strategy for the SMART survey. The benefits of this, particularly precise localization possible via high-resolution imaging, was convincingly demonstrated for early pulsar discoveries by Swainston et al (2021) and Bhat et al (2023b), where uGMRT imaging in Band 3 (300-500 MHz) and Band 4 (550-750 MHz) enabled subarcsecond-level localization for PSRs J0036−1033 and J0026 −1955.…”

“…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.…”