A recent change in the optical and γ-ray polarization of the crab nebula and pulsar
Redfern, R. M.
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Moran, P. Kyne, G.; Gouiffès, C.; Laurent, P.; Hallinan, G.; Redfern, R. M.; Shearer, A. (2015). A recent change in the optical and γ-ray polarization of the crab nebula and pulsar. Monthly Notices of the Royal Astronomical Society 456 (3), 2974-2981
We report on observations of the polarization of optical and gamma-ray photons from the Crab nebula and pulsar system using the Galway Astronomical Stokes Polarimeter (GASP), the Hubble Space Telescope, Advanced Camera for Surveys and the International Gamma-Ray Astrophysics Laboratory satellite (INTEGRAL). These, when combined with other optical polarization observations, suggest that the polarized optical emission and gamma-ray polarization changes in a similar manner. A change in the optical polarization angle has been observed by this work, from 109.5 +/- 0.degrees 7 in 2005 to 85.3 +/- 1.degrees 4 in 2012. On the other hand, the gamma-ray polarization angle changed from 115 +/- 11 degrees in 2003-2007 to 80 +/- 12 degrees in 2012-2014. Strong flaring activities have been detected in the Crab nebula over the past few years by the high-energy gamma-ray missions Agile and Fermi, and magnetic reconnection processes have been suggested to explain these observations. The change in the polarized optical and gamma-ray emission of the Crab nebula/pulsar as observed, for the first time, by GASP and INTEGRAL may indicate that reconnection is possibly at work in the Crab nebula. We also report, for the first time, a non-zero measure of the optical circular polarization from the Crab pulsar+knot system.