The High Time Resolution Universe Pulsar Survey - XVII. PSR J1325-6253, a low eccentricity double neutron star system from an ultra-stripped supernova

The observable population of double neutron star (DNS) systems in the Milky Way allow us to understand the nature of supernovae and binary stellar evolution. Until now, all DNS systems in wide orbits (P-orb > 1 d) have been found to have orbital eccentricities, e > 0.1. In this paper, we report the discovery of pulsar PSR J1325-6253: a DNS system in a 1.81-d orbit with a surprisingly low eccentricity of just e = 0.064. Through, 1.4 yr of dedicated timing with the Parkes radio telescope we have been able to measure its rate of advance of periastron, omega(over dot) = 0.. 138 +/- 0..002 yr(-1). If this induced omega(over dot) is solely due to general relativity then the total mass of the system is, M-sys = 2.57 +/- 0.06 M-circle dot. Assuming an edge-on orbit the minimum companion mass is constrained to be M-c,M- min > 0.98 M-circle dot which implies the pulsar mass is M-p,M- max < 1.59 M-circle dot. Its location in the P-(P)over dot diagram suggests that, like other DNS systems, PSR J1325-6253 is a recycled pulsar and if its mass is similar to the known examples (>1.3 M-circle dot), then the companion neutron star is probably less than similar to 1.25 M-circle dot and the system is inclined at about 50 degrees-60 degrees. The low eccentricity along with the wide orbit of the system strongly favours a formation scenario involving an ultra-stripped supernova explosion.

Automated summary

This paper reports the discovery of a double neutron star system with a surprisingly low eccentricity. By studying this system, we can gain insights into the nature of supernovae and binary stellar evolution. Measurements of the system's rate of advance and total mass suggest that it is a recycled pulsar.