Evolutionary Map of the Universe: A pilot survey to detect high Galactic latitude pulsars in variance images with ASKAP

TL;DR

This study demonstrates that variance imaging with ASKAP can effectively detect high Galactic latitude pulsars, including new discoveries, by identifying their unique scintillation signatures in a large radio survey.

Contribution

The paper introduces the use of variance imaging to detect pulsars in continuum surveys, successfully identifying known and new pulsars in ASKAP data.

Findings

Detected 20 highly variable sources, including 3 new pulsars.

Discovered two strongly scintillating pulsars with specific periods and DMs.

Proved variance imaging as a promising method for pulsar detection in large surveys.

Abstract

It has been proposed that radio pulsars can be distinguished from other point-like radio sources in continuum images by their unique interstellar scintillation signatures. Using data from the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey, we conducted a pilot survey of radio pulsars at high Galactic latitude regions via the variance imaging method. Out of approximately 59,800 compact radio sources detected in a ~480 square degree survey area, we identified 20 highly variable sources. Among them, 9 are known pulsars, 1 is a known radio star, 1 is an ultra-long period source, 3 are radio star candidates, and the remaining 6 are pulsar candidates. Notably, we discovered two strongly scintillating pulsars: one with a period of 85.707 ms and a dispersion measure (DM) of 19.4 pc/cm^3, and another with a period of 5.492 ms and a DM of 29.5 pc/cm^3. In addition, a third pulsar was discovered in the variance images, with a period of 14.82 ms and a DM of 39.0 pc/cm^3. This source shows a steep radio spectrum and a high degree of circular polarisation. These results underscore the strong potential of variance imaging for pulsar detection in full EMU and future radio continuum surveys planned with Square Kilometre Array (SKA).