Hiccups in the Night: X-ray Monitoring of the Two Crab-like LMC Pulsars

We are undertaking an extensive X-ray monitoring campaign of the two Crab-like pulsars in the Large Magellanic Clouds, PSR B0540-69 and PSR J0537-6910. We present our current phase-connected timing analysis derived from a set of 50 pointed X-ray observations spanning several years. From our initial 1.2 yr monitoring program of the young 50 ms pulsar PSR B0540-69, we find the first compelling evidence for a glitch in its rotation. This glitch is characterized by ∆ν/ν = (1.90 ± 0.05) × 10 and ∆ν̇/ν̇ = (8.5 ± 0.5) × 10. Taking into account the glitch event, we derive a braking index of n = 1.81 ± 0.07, significantly lower than previous reported. For the 16 ms pulsar, PSR J0537-6910, we recorded 6 large glitch events during a period of nearly 3 years, the highest rate of all known Crab-like systems. Despite the extreme timing activity, the long term spin-down of this pulsar continues to average −1.9743× 10 Hz/s.