Measuring the crust-superfluid coupling time-scale for 105 UTMOST pulsars with a Kalman filter (2511.15134v1)

Abstract: Crust-superfluid coupling plays an important role in neutron star rotation, particularly with respect to timing noise and glitches. Here, we present new timing-noise-based estimates of the crust-superfluid coupling time-scale (τ) for 105 radio pulsars in the UTMOST dataset, by Kalman filtering the pulse times of arrival. The 105 objects are selected because they favor a two-component, crust-superfluid model over a one-component model with log Bayes factor (\ln \mathfrak{B}{\rm BF} \geq 5). The median estimate of (τ) ranges from (10^{4.6\pm0.4})\,s for PSR J2241$-$5236 to (10^{7.7^{+0.7}{-0.4}})\,s for PSR J1644$-$4559 among 28 out of 105 objects with sharply peaked (τ) posteriors. A hierarchical Bayesian analysis is performed on 101 out of 105 objects that are canonical (i.e.\ neither recycled nor magnetars) and reside in the populous core of the (Ω{\rm c})-(\dotΩ{\rm c}) plane. It returns the population-level scaling (τ\propto Ω{\rm c}^{0.19^{+0.50}{-0.52}} |\dotΩ{\rm c}|^{0.18^{+0.18}{-0.19}}), where (Ω{\rm c}) and (\dotΩ{\rm c}) are the angular velocity and spin-down rate of the crust respectively. The variances of the stochastic crust and superfluid torques are also estimated hierarchically, with (Q_{\rm c} \propto Ω{\rm c}^{1.23^{+0.80}{-0.75}} |\dotΩ{\rm c}|^{0.49^{+0.27}{-0.32}}) and (Q_{\rm s} \propto Ω{\rm c}^{0.71^{+0.76}{-0.78}} |\dotΩ{\rm c}|^{1.27^{+0.30}{-0.28}}) respectively. Implications for the physical origin of crust-superfluid coupling, e.g.\ through mutual friction, are discussed briefly.