Long-term rotational and emission variability of 17 radio pulsars

With the ever-increasing sensitivity and timing baselines of modern radio telescopes, a growing number of pulsars are being shown to exhibit transitions in their rotational and radio emission properties. In many of these cases, the two are correlated with pulsars assuming a unique spin-down rate ( ν) for each of their specific emission states. In this work, we revisit 17 radio pulsars pre viously sho wn to exhibit spin-do wn rate v ariations. Using a Gaussian process regression (GPR) method to model the timing residuals and the evolution of the profile shape, we confirm the transitions already observed and reveal new transitions in 8 yr of extended monitoring with greater time resolution and enhanced observing bandwidth. We confirm that seven of these sources show emission-correlated νtransitions ( Δ ν), and we characterize this correlation for one additional pulsar, PSR B1642 -03. We demonstrate that GPR is able to reveal extremely subtle profile variations given sufficient data quality. We also corroborate the dependence of Δ νamplitude on νand pulsar characteristic age. Linking Δ νto changes in the global magnetospheric charge density Δρ, we speculate that νtransitions associated with large Δρvalues may be exhibiting detectable profile changes with impro v ed data quality, in cases where they have not previously been observed.