The deep observation of the Crab pulsar in the X-ray polarization: a possible polarization variation?

The Crab pulsar, a highly magnetized and rapidly rotating neutron star located at centre of the Crab pulsar wind nebula, serves as a key laboratory for probing high-energy emission and particle acceleration in pulsar magnetospheres. Although extensively studied, the underlying radiation mechanisms remain poorly constrained. X-ray polarimetry offers a powerful diagnostic of magnetic field geometry and emission regions. Using the Imaging X-ray Polarimetry Explorer, we performed precise X-ray polarization measurements of the Crab pulsar. We find a possible variation in the polarization degree of the main peak, decreasing from 16.6 per cent to 8.7 per cent in the 2–6 keV band with a confidence level of 3.3$\sigma$, while the X-ray flux, pulse profile, and spin-down rate remain stable. These results provide new evidence for intrinsic polarization variability, offering insights into dynamic processes in the pulsar magnetosphere.