2003-2018 Monitoring of the Crab Nebula Polarization in hard X-rays with INTEGRAL SPI

Abstract

We have analyzed 16 years of observations dedicated to the Crab (pulsar + nebula) with the INTEGRAL SPI instrument to investigate its polarization properties. We find that the source presents a substantially polarized emission (PF = 24%) in the hard X-ray domain, with the electric vector aligned with the pulsar spin axis, in agreement with other results at various wavelengths. The stability of the polarization characteristics with energy and over the 16 years covered by the data is remarkable, completing the standard candle status of the source in the spectral domain. The polarization measurements imply that the synchrotron emission is the dominant mechanism of photon production from radio to hard X-rays. The high level of polarized emission points out the steadiness of the source, in particular of the magnetic field configuration and geometry.

Accepted for publication in the Astrophysical Journal

References in corpus (2)

• Polarization of the Crab pulsar and nebula as observed by the Integral/IBIS telescope
• Optical polarisation of the Crab pulsar: precision measurements and comparison to the radio emission

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• In-flight calibration of the INTEGRAL/IBIS Compton mode: Application to the Crab Nebula polarization
• Performance of the X-Calibur Hard X-Ray Polarimetry Mission during its 2018/19 Long-Duration Balloon Flight