Variable spin-down in the soft gamma repeater SGR 1900+14 and correlations with burst activity

we have analyzed Rossi X-ray Timing Explorer Proportional Counter Array observations of the pulsed emission from SGR 1900+14 during 1996 September, 1998 June-October; and early 1999. Using these measurements and results reported elsewhere, we construct a period history of dais source for 2.5 yr. We find significant deviations from a steady spin-down trend during quiescence and the hurst active interval Burst and Transient Source Experiment observations of the burst emission are presented and correlations between the burst and Transient and spin-down Tate of SGR 1900+14 are discussed We find an 80 day interval during the summer of 1998 when the average spin-down rate is larger than the rate elsewhere by a factor similar to 2.3. This enhanced spin-down may be the result of a discontinuous spin-down event or "braking glitch" at the time of the giant flare on 1998 August 27. Furthermore, we find a large discrepancy between the pulsar period and average spin-down rate in X-rays as compared to radio observations for 1998 December and 1999 January.