The FAST Galactic Plane Pulsar Snapshot Survey: IV. Timing results of 30 FAST-GPPS discovered pulsars

Abstract

Timing observations are crucial for determining the basic parameters of newly discovered pulsars. Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) with the L-band 19-beam receiver covering the frequency range of 1.0 -- 1.5 GHz, the FAST Galactic Plane Pulsar Snapshot (GPPS) survey has discovered more than 600 faint pulsars with flux densities of only a few or a few tens of $\mu$Jy at 1.25 GHz. To obtain accurate position, spin parameters, dispersion measure, and to calculate derived parameters such as characteristic age and surface magnetic fields, we collect available FAST pulsar data obtained either through targeted following-up observations or coincidental survey observations with one of the 19 beams of the receiver. From these data we get the time of arrival (TOA) measurements for 30 newly discovered pulsars as well as 13 known pulsars. We demonstrate that the TOA measurements acquired by the FAST from any beams of the receiver in any observation mode (e.g., the tracking mode or the snapshot mode) can be combined together to get timing solutions. We update the ephemeris of 13 previously known pulsars and obtain the first phase-coherent timing results for 30 isolated pulsars discovered in the FAST GPPS survey. Notably, PSR J1904+0853 is an isolated millisecond pulsar, PSR J1906+0757 is a disrupted recycled pulsar, and PSR J1856+0211 has a long period of 9.89 s that can constrain pulsar death lines. Based on these timing solutions, all available FAST data have been added together to get the best pulse profiles for these pulsars.Comment: 12 pages, 7 figures. Accepted for publication in MNRA