Radio timing constraints on the mass of the binary pulsar PSR J1528−3146

¹ Laboratoire de Physique et Chimie de l’Environnement et de l’Espace, Université d’Orléans/CNRS, 45071 Orléans Cedex 02, France
e-mail: anais.berthereau@cnrs-orleans.fr
² Observatoire Radioastronomique de Nançay, Observatoire de Paris, Université PSL, Université d’Orléans, CNRS, 18330 Nançay, France
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁴ LUTH, Observatoire de Paris, Université PSL, Université Paris Cité, CNRS, 92195 Meudon, France
⁵ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218 Hawthorn, Vic 3122, Australia
⁶ ARC Centre of Excellence for Gravitational Wave Discovery, OzGrav, Mail H29, Swinburne University of Technology, PO Box 218 Hawthorn, VIC 3122, Australia
⁷ Australia Telescope National Facility, CSIRO, Space and Astronomy, PO Box 76 Epping, NSW 1710, Australia

Received: 23 February 2023
Accepted: 12 April 2023

Abstract

Context. PSR J1528−3146 is a 60.8 ms pulsar orbiting a heavy white dwarf (WD) companion, with an orbital period of 3.18 d. The pulsar was discovered in the early 2000 s in a survey at 1.4 GHz of intermediate Galactic latitudes conducted with the Parkes radio telescope. The initial timing analysis of PSR J1528−3146, using data recorded from 2001 and 2004, did not reveal any relativistic perturbations to the orbit of the pulsar or to the propagation of its pulses. However, with an orbital eccentricity of ∼0.0002 and a large companion mass on the order of 1 M_⊙, this system has been deemed likely to exhibit measurable perturbations.

Aims. This work is aimed at characterizing the pulsar’s astrometric, spin, and orbital parameters by analyzing timing measurements conducted at the Parkes, MeerKAT, and Nançay radio telescopes over nearly two decades. The measurement of post-Keplerian perturbations to the pulsar’s orbit can be used to constrain the masses of the two component stars of the binary and, in turn, to offer insights into the history of the system.

Methods. We analyzed timing data from the Parkes, MeerKAT, and Nançay radio telescopes collected over about 16 yr, obtaining a precise rotation ephemeris for PSR J1528−3146. A Bayesian analysis of the timing data was carried out to constrain the masses of the two components and the orientation of the orbit. We further analyzed the polarization properties of the pulsar to constrain the orientation of the magnetic axis and of the line of sight with respect to the spin axis.

Results. We measured a significant rate of advance of periastron, for the first time, and we set constraints on the Shapiro delay in the system and on the rate of change of the projected semi-major axis of the pulsar’s orbit. The Bayesian analysis yielded measurements for the pulsar and companion masses of M_p = 1.61_−0.13^+0.14 M_⊙ and M_c = 1.33_−0.07^+0.08 M_⊙ (68% C.L.), respectively, confirming that the companion is indeed massive. This companion mass as well as other characteristics of PSR J1528−3146 indicate that this pulsar is very similar to PSR J2222−0137, a 32.8 ms pulsar orbiting a WD whose heavy mass (∼1.32 M_⊙) has been considered unique among pulsar-WD systems until now. Our measurements suggest common evolutionary scenarios for PSRs J1528−3146 and J2222−0137.