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20th 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. Mass exchange and tidal effects mean that in close systems, the pre-supernova orbit was almost certainly circular, and therefore the final orbital parameters give us an insight into the mass lost in the second supernova explosion, and the magnitude of any asymmetric kicks imparted to the new-born neutron star. Until now, all DNS systems in wide orbits (orbital period > 1 day) have been found to have orbital eccentricities, e > 0.1 (where e = 0 is a circle, and as e increases towards 1 the orbit becomes more and more elliptical). 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 bottom panel shows the frequency-phase plot of PSR J1325−6253 across a large portion of UWL band (1200–4000 MHz), obtained by a 7.4-h observation. The intensity values in this plot are saturated at the fifth percentile. The de-dispersed flux and polarization calibrated pulse profile is shown in middle panel where the total intensity is represented by the black line. Red and blue lines represent linear and circular polarizations respectively. The top panel represents position angle (PA) in the leading edge of the pulse profile derived from the linearly polarized flux.

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