Kavli Affiliate: Nicola Omodei
| First 5 Authors: Josephine Wong, Tsunefumi Mizuno, Niccoló Bucciantini, Roger W. Romani, Yi-Jung Yang
| Summary:
We present Crab X-ray polarization measurements using IXPE data with a total
exposure of 300ks, three times more than the initial 2022 discovery paper.
Polarization is detected in three times more pulsar phase bins, revealing an
S-shaped $+40^circ$ polarization angle sweep in the main pulse and
${>}1sigma$ departures from the OPTIMA optical polarization in both pulses,
suggesting different radiation mechanisms or sites for the polarized emission
at the two wavebands. Our polarization map of the inner nebula reveals a
toroidal magnetic field, as seen in prior IXPE analyses. Along the southern
jet, the magnetic field orientation relative to the jet axis changes from
perpendicular to parallel and the polarization degree decreases by ${sim}6%$.
These observations may be explained by kink instabilities along the jet or a
collision with a dense, jet-deflecting medium at the tip. Using
spectropolarimetric analysis, we find asymmetric polarization in the four
quadrants of the inner nebula, as expected for a toroidal field geometry, and a
spatial correlation between polarization degree and photon index.
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