Timing of young radio pulsars I: Timing noise, periodic modulation and proper motion.

The smooth spin-down of young pulsarsis perturbed by two non-deterministic phenomenon, glitchesand timing noise. Although the timing noise provides insights into nuclear and plasma physics at extreme densities, it acts as a barrier to high-precision pulsartiming experiments. An improved methodology based on Bayesian inferenceis developed to simultaneously model the stochastic and deterministic parameters for a sample of 85 high-$\dot{E}$ radio pulsarsobserved for $\sim$ 10 years with the 64-m Parkes radio telescope. Timing noise is known to be a red process and we develop a parametrization based on the red-noise amplitude ($A_{\rm red}$) and spectral index($\beta$). We measure the median $A_{\rm red}$ to be $-10.4^{+1.8}_{-1.7}$ yr$^{3/2}$ and $\beta$ to be $-5.2^{+3.0}_{-3.8}$ and show that the strength of timing noise scales proportionally to $\nu^{1}|\dot{\nu}|^{-0.6\pm0.1}$, where $\nu$ is the spin frequency of the pulsarand $\dot{\nu}$ its spin-down rate. Finally, we measure significant braking indices for 19 pulsars, proper motionsfor two pulsarsand discuss the presence of periodic modulation in the arrival times of five pulsars.