Timing observations of three Galactic millisecond pulsars

We report observed and derived timing parameters for three millisecond pulsars (MSPs) from observations collected with the Parkes 64-m telescope, Murriyang. The pulsars were found during reprocessing of archival survey data by Mickaliger et al. One of the new pulsars (PSR J1546-5925) has a spin period P = 7.8ms and is isolated. The other two (PSR J0921-5202 with P = 9.7ms and PSR J1146-6610 with P = 3.7ms) are in binary systems around low-mass (>0.2 M-circle dot) companions. Their respective orbital periods are 38.2 and 62.8d. While PSR J0921-5202 has a low orbital eccentricity e = 1.3 x 10(-5), in keeping with many other Galactic MSPs, PSR J1146-6610 has a significantly larger eccentricity, e = 7.4 x 10(-3). This makes it a likely member of a group of eccentric MSP-helium white dwarf binary systems in the Galactic disc whose formation is poorly understood. Two of the pulsars are co-located with previously unidentified point sources discovered with the Fermi satellite's Large Area Telescope, but no gamma-ray pulsations have been detected, likely due to their low spin-down powers. We also show that, particularly in terms of orbital diversity, the current sample of MSPs is far from complete and is subject to a number of selection biases.

Automated summary

This study reports timing parameters for three millisecond pulsars observed with the Parkes 64-m telescope, Murriyang. One of the new pulsars is isolated, while the other two are in binary systems with low-mass companions. The study also highlights the incomplete nature of the current sample of MSPs and the presence of selection biases.