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Abstract:

We use data from the MeerTime project on the MeerKAT telescope to ask whether the radio emission properties of millisecond pulsars (MSPs) and slowly rotating, younger pulsars (SPs) are similar or different. We show that the flux density spectra of both populations are similarly steep, and the widths of MSP profiles obey the same dependence on the rotational period as slow pulsars. We also show that the polarization of MSPs has similar properties to slow pulsars. The commonly used pseudo-luminosity of pulsars, defined as the product of the flux density and the distance squared, is not appropriate for drawing conclusions about the relative intrinsic radio luminosity of SPs and MSPs. We show that it is possible to scale the pseudo-luminosity to account for the pulse duty cycle and the solid angle of the radio beam, in such a way that MSPs and SPs do not show clear differences in intrinsic luminosity. The data therefore support common emission physics between the two populations in spite of orders of magnitude difference in their period derivatives and inferred, surface, dipole magnetic field strengths.

Abstract:

We report here on the timing of 597 pulsars over the last four years with the MeerKAT telescope. We provide times of arrival, pulsar ephemeris files, and per-epoch measurements of the flux density, dispersion measure (DM), and rotation measure (RM) for each pulsar. In addition, we use a Gaussian process to model the timing residuals to measure the spin frequency derivative at each epoch. We also report the detection of 11 glitches in nine individual pulsars. We find significant DM and RM variations in 87 and 76 pulsars, respectively. We find that the DM variations scale approximately linearly with DM, which is broadly in agreement with models of the ionized interstellar medium. The observed RM variations seem largely independent of DM, which may suggest that the RM variations are dominated by variations in the interstellar magnetic field on the line of sight, rather than varying electron density. We also find that normal pulsars have around 5 times greater amplitude of DM variability compared to millisecond pulsars, and surmise that this is due to the known difference in their velocity distributions.

Abstract:

The S-shaped swing of the linear polarization position angle (PPA) observed in many pulsars can be interpreted by the rotating vector model (RVM). However, efforts to fit the RVM for a large sample of pulsars observed with the MeerKAT telescope as a part of the Thousand-Pulsar-Array (TPA) programme, only succeeded for about half the cases. High time-resolution studies suggest that the failed cases arise due to the presence of orthogonal polarization modes, or highly disordered distribution of PPA points. One such example is PSR J1645−0317. Recently it has been shown that the RVM can be recovered in this pulsar by using only time samples which are greater than 80 per cent linearly polarized. In this work, we test this novel approach on the brightest 249 pulsars from the TPA sample, of which 177 yield sufficient highly polarized samples to be amenable to our method. Remarkably, only nine of these pulsars (5 per cent) now fail to fit the RVM as opposed to 59 per cent from the original analysis. This result favours the paradigm that the underlying mechanism is coherent curvature radiation.