Are fast radio bursts wandering narrow beams?

It is generally assumed that the sources of fast radio bursts (FRB) radiate roughly isotropically, so that the observed low duty cycle of any individual source indicates a similar low duty cycle of its radio-frequency emission. An alternative hypothesis is that the radiative duty cycle is O(1),but that the radiation is emitted in a beam with a solid angle comparable to the observed duty cycle, whose direction wanders or sweeps across the sky. This hypothesis relaxes the extreme power demands of isotropically radiating models of FRB at the price of multiplying the number of sources. The constraints on pulsar models are relaxed; rather than being unprecedentedly fast-spinning and highly magnetized with short spin-down times, their parameters may be closer to those of typical radio pulsars. In general, it is not possible to distinguish intermittent isotropic emission from wandering beams on purely phenomenological grounds.