Anti-glitch: Transient or Permanent, a Bayesian View

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Abstract:: Recently, Archibald et al. (2013) reported observing a sudden spin-down or anti-glitch in the rotation of magnetar 1E 2259+586. Such events are rare; however this particular anti-glitch was followed by another event which Archibald et al. (2013) suggested could either be a conventional glitch or another anti-glitch. In this paper we apply Bayesian Model Selection to quantitatively determine which of these two latter events better explains the observed data. We show that two successive anti-glitch events is the favoured explanation (with a Bayes Factor of $\sim 45$ ) when compared to model consisting of an anti-glitch followed by a glitch. Further, we show that the second anti-glitch has in associated frequency change, $\Delta\nu$ of $-8.15 \times 10^{-8}$ Hz. We discuss the implications of these results on possible physical mechanisms behind this anti-glitch.

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LIGO Document P1300203-v1