Publication Date:
2016-01-02
Description:
We report on observations of the polarization of optical and -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 -ray polarization changes in a similar manner. A change in the optical polarization angle has been observed by this work, from 109.5 ± 0 $_{.}^{\circ}$ 7 in 2005 to 85.3 ± 1 $_{.}^{\circ}$ 4 in 2012. On the other hand, the -ray polarization angle changed from 115 ± 11° in 2003–2007 to 80 ± 12° in 2012–2014. Strong flaring activities have been detected in the Crab nebula over the past few years by the high-energy -ray missions Agile and Fermi , and magnetic reconnection processes have been suggested to explain these observations. The change in the polarized optical and -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.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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