Magnetic-field structure of the Crab pulsar wind nebula revealed with IXPE

Mizuno Tsunefumi

Ohno Hiroshi

Watanabe Eri

Bucciantini Niccolò

Gunji Shuichi

Shibata Sinpei

Slane Patrick

Weisskopf Martin C.

Publications of the Astronomical Society of Japan

We report a detailed study of the magnetic-field structure of the Crab pulsar wind nebula, using the X-ray polarization data in 2–8 keV obtained with the Imaging X-ray Polarimetry Explorer. Contamination of the data for the nebula region by the pulsar emission was removed through application of a stringent pulsation phase cut, extracting a phase range of 0.7–1.0 only. We found that the electric-field vector polarization angle (PA) was about 130○ from north to east with a polarization degree (PD) of about 25% at the pulsar position, indicating that the direction of the toroidal magnetic field is perpendicular to the pulsar spin axis in the region close to the termination shock. The PA gradually deviated from the angle as an increasing function of the distance from the pulsar. There was a region of low PD to the west of the X-ray torus. Although such a region is expected to be located at the torus edge, where geometrical depolarization due to a steep spatial variation of the PA is expected, the observed low-PD region positionally deviated from the edge. We found that the region of low PD positionally coincided with a dense filament seen in the optical band, and conjecture that the low-PD region may be produced through deflection of the pulsar wind. By comparing the values of the PD at the pulsar position between the data and a model, in which toroidal and turbulent magnetic fields were considered, we estimated the fractional energy of the turbulent magnetic field to be about 23 of the total. We also evaluated the potential polarization of the northern jet in the nebula and derived the PD and PA to be about 30% and 120○, respectively.

eng

Oxford

This is a pre-copyedited, author-produced version of an article accepted for publication in Publications of the Astronomical Society of Japan following peer review. The version of record Tsunefumi Mizuno, Hiroshi Ohno, Eri Watanabe, Niccolò Bucciantini, Shuichi Gunji, Sinpei Shibata, Patrick Slane, Martin C Weisskopf, Magnetic-field structure of the Crab pulsar wind nebula revealed with IXPE, Publications of the Astronomical Society of Japan, Volume 75, Issue 6, December 2023, Pages 1298–1310 is available online at: https://doi.org/10.1093/pasj/psad070.

This is not the published version. Please cite only the published version.

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[DOI] https://doi.org/10.1093/pasj/psad070 isVersionOf

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