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21st of June 2022
PSR J1325-6253, a low eccentricity double neutron star system
by Sengar et al.
Double neutron star (DNS) systems are one of the most important classes of objects used to test and understand numerous astrophysical and fundamental physics phenomena, including general relativity (GR) in the strong-field regime. These systems essentially consist of two-point masses, whose orbital motion and evolution are well defined by GR. Sengar et al. report the discovery with the Parkes 64m radio-telescope, Murriyang, of the pulsar PSR J1325−6253: a DNS system in a 1.81 day orbit with a surprisingly low eccentricity of just e = 0.064. The figure above shows the mass–mass diagram for PSR J1325−6253 showing constraints on the pulsar mass and the companion mass. The panels on the top and to the right show the probability distribution functions for the pulsar and companion masses assuming an isotropic inclination distribution (in light blue) and distribution using the astrophysical priors (pink). The grey region in the main panel is excluded due to the constraint on the binary mass function corresponding to the maximum possible orbital inclination angle. Other black dotted lines represent companion mass limits for various orbital inclinations. The solid blue line represent the measured rate of periastron advance and the dotted blue lines represent the +/-1𝜎 uncertainty range. The vertical and horizontal dashed black lines correspond to the minimum and maximum pulsar and companion masses among the known DNS systems for which both masses are well measured. The well-measured masses for individual DNS systems are shown in blue points. The authors conclude that PSR J1325-6253 is a recycled pulsar and, if its mass is similar to other known examples (>1.3 solar masses), then the companion neutron star is probably less than ~1.25 solar masses and the system is inclined at about 50--60 degrees. The low eccentricity along with the wide orbit of the system strongly favours a formation scenario involving an ultra-stripped supernova explosion.

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