Globular Clusters GMRT Pulsar Search (GCGPS). II. Discovery of Five Millisecond Pulsars in M69 and M70

Journal article

This paper reports recent discoveries from the Globular Clusters GMRT Pulsar Search 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° < δ < –17°), excluding the declination range that can be covered by the Five-hundred-meter Aperture Spherical radio Telescope. 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 five millisecond pulsars (MSPs) in two GCs, NGC 6637 (Messier69/M69) and NGC 6681 (Messier70/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), one of which (M69A) we localize with arcsecond precision using interferometric imaging and targeted follow-up, and the other (M69B) remains unlocalised due to sensitivity constraints. 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 nondetections, we report upper limits on pulsed emission based on the rms noise levels in the image plane.

Authors: Das, J; Roy, J; Freire, PCC; Ransom, S; Bhattacharyya, B

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: The Astrophysical Journal
• Volume: 1000
• Issue: 1
• Pages: 116
• Article number: 116
• Publication date: 2026-03-17
• Acceptance date: 2026-02-16
• DOI: 10.3847/1538-4357/ae473b
• EISSN: 1538-4357
• ISSN: 0004637X, 0004-637X
• Language: English
• Keywords: Globular star clusters; Radio astronomy; Neutron stars; Binary pulsars; Millisecond pulsars