Fast Radio Bursts (FRBs) are intense, millisecond-duration broadband radio
transients, the emission mechanisms of which are not understood. Masui et al.
recently presented Green Bank Telescope observations of FRB 110523, which
displayed temporal variation of the linear polarisation position angle (PA).
This effect is commonly seen in radio pulsars and is attributed to a changing
projected magnetic field orientation in the emission region as the star
rotates. If a neutron star is the progenitor of this FRB, and the emission
mechanism is pulsar-like, we show that the progenitor is either rapidly
rotating, or the emission originates from a region of complex magnetic field
geometry. The observed PA variation could also be caused by propagation effects
within a neutron-star magnetosphere, or by spatially varying magnetic fields if
the progenitor lies in a dense, highly magnetised environment. Although we urge
caution in generalising results from FRB 110523 to the broader FRB population,
our analysis serves as a guide to interpreting future polarisation measurements
of FRBs, and presents another means of elucidating the origins of these
enigmatic ephemera.Comment: 7 pages, 2 figures, submitted to MNRA
