Session 36. Isolated Pulsars
Oral, Thursday, November 9, 2000, 1:00-2:30pm, Pago Pago Ballroom

## [36.06] Timing results from the 16 ms pulsar, J0537-6910 in N157B

J. Middleditch (LANL), F. E. Marshall, W. Zhang (NASA/GSFC), E. V. Gotthelf (Columbia), Q. D. Wang (UMass)

We present a status report on our on-going intensive RXTE monitoring campaign of PSR J0537-6910 begun in Jan 1999. PSR J0537-6910 is the 16 ms Crab-like X-ray pulsar in the LMC discovered in 1998 with the Rossi X-ray Timing Explorer (RXTE). This timing campaign reveals three large glitches'' in the pulsar's spindown which occurred at approximately six month intervals, each resulting in a ~ 0.5 \times 10-6 relative increase of the pulse frequency. Although PSR J0537-6910 is the oldest and most rapidly rotating Crab-like pulsar, this rate of glitching now appears to be the highest of all known Crab-like systems. With the exception of the Jan 2000 observations, we are able to maintain the cycle-count of the pulse period for all data between the glitches. The long term spindown of the pulsar continues to average -1.9743 \times 10-10 Hz/s, i.e., the same value previously reported from the discovery observations. With continued monitoring we can determine the braking index, n, of the power law describing the decline of the spin frequency of J0537-6910; this may allow us to distinguish between possible physical mechanisms contributing to the spindown. JM thanks the University of California Institute for Nuclear and Particle Astrophysics and Cosmology (INPAC) for funding.