Kavli Affiliate: Renxin Xu
| First 5 Authors: Shi Dai, Jiguang Lu, Chen Wang, Weiyang Wang, Renxin Xu
| Summary:
Fast spinning (e.g., sub-second) neutron star with ultra-strong magnetic
fields (or so-called magnetar) is one of the promising origins of repeating
fast radio bursts (FRBs). Here we discuss circularly polarised emissions
produced by propagation effects in the magnetosphere of fast spinning
magnetars. We argue that the polarisation-limiting region is well beyond the
light cylinder, suggesting that wave mode coupling effects are unlikely to
produce strong circular polarisation for fast spinning magnetars. Cyclotron
absorption could be significant if the secondary plasma density is high.
However, high degrees of circular polarisation can only be produced with large
asymmetries in electrons and positrons. We draw attention to the non-detection
of circular polarisation in current observations of known repeating FRBs. We
suggest that the circular polarisation of FRBs could provide key information on
their origins and help distinguish different radiation mechanisms.
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