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Discovery of Millisecond Pulsars toward the Galactic Bulge in an Image-based Survey with MeerKAT

Rahul Sengar, Akash Anumarlapudi, David L. Kaplan, Dale A. Frail, Scott D. Hyman, Emil Polisensky

Abstract

We report on the follow-up observations of circularly polarized sources identified in the MeerKAT image-based survey of the Galactic bulge. Using the Parkes radio telescope, we observed sixteen circularly polarized sources with the UWL receiver and detected nine pulsars, six of which are new discoveries. All pulsars are fast rotators with spin periods under 100 ms. Among the new discoveries, five are millisecond pulsars (MSPs) and one has a spin period of 53.6 ms. At least four new MSPs exhibit clear signs of binary motion in their discovery observations. The dispersion measures (DMs) of these pulsars fall between 18 and 330 pc cm$^{-3}$, which are lower than expected for Galactic bulge members and indicate that these pulsars lie in the foreground along the line of sight rather than within the bulge itself. This is the first time such a large number of pulsars have been confirmed from candidates identified in an image-based survey. These discoveries underscore the exceptional efficacy of circular polarization selection in image-based pulsar surveys, and demonstrate the powerful synergy between high-sensitivity imaging and targeted time-domain follow-up using wide-band receivers, and strengthen prospects for future deep pulsation searches$-$e.g., with MeerKAT or the forthcoming SKA or DSA-2000$-$to uncover the true millisecond pulsar population in the Galactic bulge.

Discovery of Millisecond Pulsars toward the Galactic Bulge in an Image-based Survey with MeerKAT

Abstract

We report on the follow-up observations of circularly polarized sources identified in the MeerKAT image-based survey of the Galactic bulge. Using the Parkes radio telescope, we observed sixteen circularly polarized sources with the UWL receiver and detected nine pulsars, six of which are new discoveries. All pulsars are fast rotators with spin periods under 100 ms. Among the new discoveries, five are millisecond pulsars (MSPs) and one has a spin period of 53.6 ms. At least four new MSPs exhibit clear signs of binary motion in their discovery observations. The dispersion measures (DMs) of these pulsars fall between 18 and 330 pc cm, which are lower than expected for Galactic bulge members and indicate that these pulsars lie in the foreground along the line of sight rather than within the bulge itself. This is the first time such a large number of pulsars have been confirmed from candidates identified in an image-based survey. These discoveries underscore the exceptional efficacy of circular polarization selection in image-based pulsar surveys, and demonstrate the powerful synergy between high-sensitivity imaging and targeted time-domain follow-up using wide-band receivers, and strengthen prospects for future deep pulsation searchese.g., with MeerKAT or the forthcoming SKA or DSA-2000to uncover the true millisecond pulsar population in the Galactic bulge.

Paper Structure

This paper contains 1 section, 1 figure.

Table of Contents

  1. Introduction

Figures (1)

  • Figure 1: Distribution of the 20 MeerKAT mosaic pointings analyzed in radio-continuum images by frail_24. The colored background shows the maximum line-of-sight DM from the YMW16 model, assuming a distance of 25 kpc. Brighter regions correspond to higher integrated electron column densities and thus higher DM. Gray crosses mark the centers of each pointing, each spanning approximately $3.125^\circ \times 3.125^\circ$. Previously known pulsars detected as polarized sources are shown as cyan points. Circularly polarized pulsar candidates are shown as stars: red stars indicate candidates not yet observed, magenta stars indicate candidates that have been observed, and filled magenta stars mark those confirmed as pulsars.