A giant glitch in the energetic 69 millisecond X-ray pulsar AXS J161730-505505

We present new results on the recently discovered 69 ms X-ray pulsar AXS J1 61730-505505, the sixth youngest example of a rotation-powered pulsar. We h ave undertaken a comprehensive X-ray-observing campaign of AXS J161730-5055 05 with the ASCA, BeppoSAX, and RXTE observatories and follow its long-term spin-down history between 1989 and 1999 using these observations and archi val Ginga and ASCA data sets. The spin-down is not simply described by a li near function as originally thought, but instead we find evidence of a gian t glitch (\Delta P/P \ greater than or equal to 10(-6)) between 1993 August and 1997 September, perhaps the largest yet observed from a young pulsar. The glitch is well described by steps in P and (P)over dot accompanied by a persistent P similar to those seen in the Vela pulsar. The pulse profile o f AXS J161730-505505 presents a single asymmetric peak that is maintained o ver all observation epochs. The energy spectrum is also steady over time, c haracterized by a highly absorbed power law with a photon index Gamma = 1.4 +/- 0.2, consistent with that found for other young rotation powered pulsa rs.