Speaker
Description
Pulsar glitches—sudden increases in the rotational frequency of neutron stars—provide a probe of matter at densities exceeding nuclear density, but most pulsars glitch only once, limiting individual studies. Ensemble analyses show a bimodal glitch-size distribution, interpreted by some as evidence for two trigger mechanisms: small glitches (<10⁷) and large glitches (>10⁷). Others argue both sizes may arise from a single mechanism. Prior studies of individual pulsars have reported power-law, lognormal, and exponential glitch-size distributions, with inter-glitch intervals generally consistent with exponentials. Using an updated glitch database, this study reexamines size and inter-glitch interval distributions, their relationship, and the possible contribution of linear creep—a non-threshold, thermally driven regime traditionally thought unable to generate glitches. Bayesian analysis confirms bimodal glitch-size distributions in J0537-6910 and the Vela pulsar. In both, bimodality reflects frequent, similarly sized large glitches and suggests two distinct size populations unique to each pulsar. Large glitches are consistent with vortices crossing larger radial distances in the nonlinear, threshold-triggered creep regime. Inter-glitch intervals in the Vela, J1341-6220, and J1801-2304 are also bimodal, indicating short intervals driven by creep and longer intervals when creep is suppressed. Other pulsars show lognormal, Gaussian, or exponential size distributions, with lognormal or exponential timing distributions. Glitch size correlates with the time to the next glitch only in pulsars dominated by large glitches. In the Vela, the correlation strengthens markedly (0.20 — 0.66) when small glitches are excluded. Random small glitches produced in the linear creep regime—modulated by temperature and turbulent superfluid flow—may explain these patterns. Overall, the results extend the coherent-noise framework, showing that bimodality in sizes and intervals can arise naturally from the coexistence of nonlinear vortex avalanches and continuous, thermally driven linear creep, unifying small and large glitches within a single physical mechanism. External spin parameters have only mild influence on glitch behavior.
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