Evidence of QED effects from the polarisation of the optical radiation from an Isolated Neutron Star

Roberto P. Mignani

RX J1856.5-3754 is a radio-quiet Isolated Neutron Star (INS) discovered in the soft X-rays through its purely thermal surface emission. Owing to its large inferred magnetic field of 10¹³G, radiation from its surface is expected to be substantially polarised, independently on the mechanism actually responsible for the thermal emission. A large observed polarisation degree is, however, expected only if quantum electrodynamics (QED) vacuum birefringence effects are active in the magnetised vacuum around the star. Here, we report on the measurement of the optical linear polarisation for RX J1856.5-3754 (V∼25.5 mag) with the Very Large Telescope. We measured a polarisation degree P.D.=16.43%±5.26%, large enough to support the effect of vacuum birefringence, as predicted by QED.

Proceedings of the Polish Astronomical Society, vol. 7, 175-180 (2018)

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