Radio and Gamma-Ray Timing of a Newly Discovered Millisecond Pulsar

Abstract

We report the discovery and timing of PSR J2147-3604, a fully recycled millisecond pulsar with a spin period of 3.2 ms, discovered in a reprocessing of the 350-MHz Green Bank North Celestial Cap (GBNCC) survey and later serendipitously confirmed by the MeerKAT TRAPUM UHF survey of Fermi-LAT unidentified sources. We followed up this pulsar with Murriyang/Parkes radio telescope and obtained a phase-connected timing solution spanning one year, revealing a 4.5-day binary orbit with very low eccentricity (e ~ 1.9 x $10^{-5}$). A follow-up search in LAT data revealed gamma-ray pulsations, allowing for a joint radio and gamma-ray timing analysis. Assuming a neutron-star mass of 1.5 Msun, the inferred median companion mass (~0.2 Msun) is consistent with a helium white dwarf. The pulsar has a low dispersion measure of 17.0 pc cm$^{-3}$ and shows strong scintillation, leading to it being detected in ~72% of the observations covering the 704-1174 MHz band with Murriyang. The pulsar has a narrow duty cycle of ~6.5%, which leads to individual time of arrival (ToA) uncertainties of ~4.5 us for a 10 min integration with MeerKAT, suggesting this pulsar is well suited for inclusion in PTA experiments.