paper

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

arXiv:2511.15134 · doi:10.1093/mnras/staf2053

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 J22415236 to \(10^{7.7^{+0.7}_{-0.4}}\)\,s for PSR J16444559 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.

15 pages of main text, 6 appendices. Accepted for publication in MNRAS

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