Mining the time axis with TRON. I. Millisecond pulsars in Omega Centauri, Terzan 5 and 47 Tucanae detected through MeerKAT interferometric imaging

TL;DR

This paper introduces TRON, a new pipeline for detecting medium-timescale radio transients and variables in archival MeerKAT data, successfully identifying known millisecond pulsars and eclipsing systems in globular clusters.

Contribution

The paper presents TRON, a novel image-plane transient detection pipeline that enables systematic mining of archival data for medium-timescale radio sources, improving detection capabilities.

Findings

Detected known eclipsing MSPs in Omega Centauri and Terzan 5.

Identified multiple MSPs and candidates in 47 Tucanae.

Confirmed eclipsing nature of a previously known MSP.

Abstract

Medium-timescale (minutes to hours) radio transients are a relatively unexplored population. The wide field-of-view and high instantaneous sensitivity of instruments such as MeerKAT provides an opportunity to probe this class of sources, using image-plane detection techniques. We aim to systematically mine archival synthesis imaging data in order to search for medium-timescale transients and variables that are not detected by conventional long-track image synthesis techniques. We deploy a prototype blind transient and variable search pipeline named TRON. This processes calibrated visibility data, constructs high-time cadence images, performs a search for variability on multiple timescales, and extracts lightcurves for detected sources. As proof of concept, we apply it to three MeerKAT observations of globular clusters, known to host transient or variable sources. We detect a previously known eclipsing MSP suspected to be a `black widow' system, in the globular cluster Omega Centauri, with a light curve confirming the eclipsing nature of the emission. We detect a previously known `red back' eclipsing MSP in the globular cluster Terzan 5. Using observations of the globular cluster 47 Tucanae, we detect two known millisecond pulsars (MSPs), and one previously reported MSP candidate, with hints of eclipsing behaviour.