MeerKAT Pulsar Timing Array parallaxes and proper motions

Abstract

Abstract We have determined positions, proper motions, and parallaxes of 77 millisecond pulsars (MSPs) from ∼3 years of MeerKAT radio telescope observations. Our timing and noise analyses enable us to measure 35 significant parallaxes (12 of them for the first time) and 69 significant proper motions. Eight pulsars near the ecliptic have an accurate proper motion in ecliptic longitude only. PSR J0955−6150 has a good upper limit on its very small proper motion (<0.4 mas yr−1). We used pulsars with accurate parallaxes to study the MSP velocities. This yields 39 MSP transverse velocities, and combined with MSPs in the literature (excluding those in Globular Clusters) we analyse 66 MSPs in total. We find that MSPs have, on average, much lower velocities than normal pulsars, with a mean transverse velocity of only 78(8) km s−1 (MSPs) compared with 246(21) km s−1 (normal pulsars). We found no statistical differences between the velocity distributions of isolated and binary millisecond pulsars. From Galactocentric cylindrical velocities of the MSPs, we derive 3-D velocity dispersions of σρ, σφ, σz = 63(11), 48(8), 19(3) km s−1. We measure a mean asymmetric drift with amplitude 38(11) km s−1, consistent with expectation for MSPs, given their velocity dispersions and ages. The MSP velocity distribution is consistent with binary evolution models that predict very few MSPs with velocities >300 km s−1 and a mild anticorrelation of transverse velocity with orbital period.