MeerKAT Pulsar Timing Array parallaxes and proper motions
arxiv(2024)
摘要
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
σ_ρ, σ_ϕ, σ_z = 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.
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