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

This is the authors' abstract. We don't add key points for this paper.

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 data set, by Kalman filtering the pulse times of arrival. The 105 objects are selected because they favour a two-component crust-superfluid model over a one-component model with log Bayes factor ln BBF ≥ 5. The median estimate of τ ranges from 104.6± 0.4 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 c–Ω ̇c plane. It returns the population-level scaling τ ∝ Ω c^0.19+0.50-0.52 |Ω ̇c|^0.18+0.18-0.19, where Ω c and Ω ̇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 Qc ∝ Ω c^1.23+0.80-0.75 |Ω ̇c|^0.49+0.27-0.32 and Qₛ ∝ Ω c^0.71+0.76-0.78 |Ω ̇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.