Glitches in Anomalous X-ray Pulsars

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Abstract
After 10 years of RXTE monitoring of 5 Anomalous X‐ray Pulsars, we report the detection of 10 glitches and 5 glitch candidates. Armed with sufficient data for a meaningful comparison of AXP and radio pulsar glitch properties, we show that in terms of fractional frequency change, AXPs are among the most actively glitching neutron stars, with glitch amplitudes in general larger than in radio pulsars. However, in terms of absolute glitch amplitude, AXP glitches are unremarkable. We show that three of the largest AXP glitches observed thus far have recoveries that are unusual among those of radio pulsar glitches, with the combination of recovery time scale and fraction yielding changes in spin‐down rates following the glitch similar to, or larger than, the long‐term average. We also observed a large long‐term fractional increase in the magnitude of the spin‐down rate of 1E 1841–045, following its largest glitch. These observations are challenging to interpret in standard glitch models, as is the frequent occurence of large glitches given AXPs' high measured temperatures. We speculate that the stellar core may be involved in the largest AXP glitches. Furthermore we show that unlike in radio pulsars, AXP glitches sometimes, but not necessarily always, involve major radiative events.

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