Spin-down rate of 1E 2259+586 from RXTE observation
  We present new X-ray observations of the X-ray pulsar 1E 2259+586, obtained during March 1997, with the Rossi X-Ray Timing Explorer (RXTE). We have measured the pulse frequency derivative $\dot \nu = (-1.08 \pm 0.04) \times 10^{-14}$ Hz s$^{-1}$ from pulse arrival times obtained in a sequence of 5 observations spread over one month. This $\dot\nu$ is consistent with the long term spin-down trend. We also found that the observed X-ray luminosity is consistent with that measured at quiescent X-ray flux levels by previous missions. Our observations imply that 1E 2259+586 was spinning down steadily without exhibiting any stochastic torque noise fluctuations during the month covered by our observations. 
A. Baykal (Physics Department, Middle East Technical University,   Ankara, Turkey), J.H. Swank, M.J. Stark, T.E. Strohmayer,...