Globular Clusters GMRT Pulsar Search (GCGPS) II: Discovery of five MSPs in M69 and M70

Abstract

This paper reports recent discoveries from the Globular Clusters GMRT Pulsar Search (GCGPS) survey, which aims to uncover pulsars in the globular clusters (GCs) of the Milky Way using the upgraded Giant Metrewave Radio Telescope (uGMRT). Utilising the Band-4 (550$-$750 MHz) and Band-3 (300$-$500 MHz) receivers, the survey targets GCs accessible to uGMRT ($-53^\circ\,<\,δ\,<\,-17^\circ$), excluding the declination range that can be covered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The survey focuses on GCs that have not previously been searched with comparable sensitivity in these radio frequencies. In this paper, we present the discovery of the five MSPs in two GCs, $-$ NGC~6637 (M69) and NGC~6681 (M70), each hosting MSPs identified here for the first time. Observations of M69 led to the discovery of two MSPs: J1831$-$3220A (M69A) and J1831$-$3220B (M69B), both of which we localize with arcsecond precision using interferometric imaging. Observations of M70 resulted in three new MSPs: J1843$-$3217A (M70A), J1843$-$3217B (M70B), and J1843$-$3217C (M70C). Although direct imaging did not yield precise localizations for these MSPs, we provide initial estimates based on uGMRT beam forming and imaging analysis. Additionally, we present preliminary imaging results for other observed GCs, and in cases of non-detections, we report upper limits on pulsed emission based on the rms noise levels in the image plane.