Discovery and timing of ten new millisecond pulsars in the globular cluster Terzan 5

¹ Max Planck Institute for Gravitational Physics (Albert Einstein Institute), 30167 Hannover, Germany
e-mail: prajwal.voraganti.padmanabh@aei.mpg.de
² Leibniz Universität Hannover, 30167 Hannover, Germany
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: pfreire@mpifr-bonn.mpg.de
⁴ National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA
e-mail: sransom@nrao.edu
⁵ INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italy
⁶ Department of Physics and Astronomy, West Virginia University, PO Box 6315, Morgantown, WV 26506, USA
⁷ Center for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USA
⁸ SETI Institute, 339 Bernardo Ave, Suite 200, Mountain View, CA 94043, USA
⁹ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122, Australia
¹⁰ South African Radio Astronomy Observatory, 2 Fir Street, Black River Park, Observatory 7925, South Africa
¹¹ George Mason University, Fairfax, VA 22030, USA
¹² High Energy Physics, Cosmology and Astrophysics Theory (HEPCAT), Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, South Africa
¹³ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
¹⁴ ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
¹⁵ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
¹⁶ Department of Physics and Astronomy, UBC, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
¹⁷ National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing 100101, PR China

Received: 22 January 2024
Accepted: 25 March 2024

Abstract

We report the discovery of ten new pulsars in the globular cluster Terzan 5 as part of the Transients and Pulsars with MeerKAT (TRAPUM) Large Survey Project. We observed Terzan 5 at L-band (856–1712 MHz) with the MeerKAT radio telescope for four hours on two epochs, and performed acceleration searches of 45 out of 288 tied-array beams covering the core of the cluster. We obtained phase-connected timing solutions for all ten discoveries, covering nearly two decades of archival observations from the Green Bank Telescope for all but one. Highlights include PSR J1748−2446ao which is an eccentric (e = 0.32) wide-orbit (orbital period P_b = 57.55 d) system. We were able to measure the rate of advance of periastron (ω̇) for this system allowing us to determine a total mass of 3.17 ± 0.02 M_⊙. With a minimum companion mass (M_c) of ∼0.8 M_⊙, PSR J1748−2446ao is a candidate double neutron star (DNS) system. If confirmed to be a DNS, it would be the fastest spinning pulsar (P = 2.27 ms) and the longest orbital period measured for any known DNS system. PSR J1748−2446ap has the second highest eccentricity for any recycled pulsar (e ∼ 0.905) and for this system we can measure the total mass (1.997 ± 0.006 M_⊙) and estimate the pulsar and companion masses, (1.700_−0.045^+0.015 M_⊙ and 0.294_−0.014^+0.046 M_⊙, respectively). PSR J1748−2446ar is an eclipsing redback (minimum M_c ∼ 0.34 M_⊙) system whose properties confirm it to be the counterpart to a previously published source identified in radio and X-ray imaging. We were also able to detect ω̇ for PSR J1748−2446au leading to a total mass estimate of 1.82 ± 0.07 M_⊙ and indicating that the system is likely the result of Case A Roche lobe overflow. With these discoveries, the total number of confirmed pulsars in Terzan 5 is 49, the highest for any globular cluster so far. These discoveries further enhance the rich set of pulsars known in Terzan 5 and provide scope for a deeper understanding of binary stellar evolution, cluster dynamics and ensemble population studies.