Hubble Space Telescope Multiepoch Imaging of the PSR B0540–69 System Unveils a Highly Dynamic Synchrotron Nebula

PSR B0540-69 is the Crab twin in the Large Magellanic Cloud. The age and energetic and overall behavior of the two pulsars are very similar. The same is true for the general appearance of their pulsar wind nebulae (PWNe). Analysis of Hubble Space Telescope images spanning 10 yr unveiled significant variability in the PWN surrounding PSR B0540-69, with a hot spot moving at ~0.04c. Such behavior, reminiscent of the variability observed in the Crab Nebula along the counterjet direction, may suggest an alternative scenario for the geometry of the system. The same data were used to assess the pulsar proper motion. The null displacement recorded over 10 yr allowed us to set a 3 σ upper limit of 290 km s-1 to the pulsar velocity.