Polarization of the Crab pulsar and nebula as observed by the Integral/IBIS telescope

TL;DR

This study uses the Integral-IBIS telescope to detect and analyze the polarization of high-energy emission from the Crab pulsar and nebula, revealing insights into their magnetic structure and wind geometry.

Contribution

It provides the first strong evidence of high-energy polarization from the Crab nebula using the IBIS telescope, confirming and extending previous findings.

Findings

Detection of strongly polarized emission at energies above 200 keV

Polarization angle aligned with the pulsar rotation axis

Extension of polarization measurements across all pulsar phases

Abstract

Neutron stars generate powerful winds of relativistic particles that form bright synchrotron nebulae around them. Polarimetry provides a unique insight into the geometry and magnetic configuration of the wind, but high-energy measurements have failed until recently. The Integral-IBIS telescope has been used in its Compton mode to search for linearly polarized emission for energies above 200 keV from the Crab nebula. The asymmetries in the instrument response are small and we obtain evidences for a strongly polarized signal at an angle parallel to the pulsar rotation axis. This result confirms the detection recently reported by Dean et al. (2008), and extends the polarization measure for all the pulsar's phases. The hard X-ray/soft $\gamma$-ray observations therefore probe the inner jets or equatorial flow of the wind. The achieved sensitivity opens a new window for polarimetric studies at energies above 200 keV.