\emph{RXTE} Timing Analysis of the AXP 1E 2259+586

TL;DR

This paper analyzes RXTE observations of the AXP 1E 2259+586 from 2002 to 2010, studying glitch recoveries, frequency shifts, and unusual events in its spin-down behavior.

Contribution

It provides detailed timing analysis of the 2002 and 2007 glitches, revealing that the recovery fits a two-exponential model and identifying microglitch-like frequency shifts.

Findings

Recovery of 2002 glitch fits a two-exponential model

Detected two microglitch-like frequency shifts

Observed fractional frequency change of approximately 8.2×10⁻⁷

Abstract

We report the pulse timing analysis of \emph{Rossi X-ray Timing Explorer} (\emph{RXTE}) observations of the anomalous X-ray pulsar 1E 2259+586 from its 2002 outburst to October, 2010. Our objectives are to extend the work on the recovery stage after the 2002 glitch, investigate the variations caused by the second glitch which occurred in 2007 and look for other unusual events, if any, that arise in the regular spin-down trend of the source. The recovery of the 2002 glitch gives good fit when the two-exponential glitch model of the Crab pulsar is used, rather than the standard glitch model, in the 1360-day interval after the first glitch. The sampling of the following 260-day is not frequent enough to be phase-connected. After that interval, our timing analysis yields that there is a fractional frequency change of $\frac{\Delta\nu}{\nu}\sim8.20(2)\times10^{-7}$. Moreover, we report two frequency shifts of fractional changes, $\frac{\Delta\nu}{\nu}\sim3\times10^{-8},-1\times10^{-8}$: The first one at MJD $\sim53750$ had a positive fractional frequency change in contrast to the second one at MJD $\sim54880$ for which the pulse frequency decreased. These frequency shifts both resemble the microglitches observed in radio pulsars.