Periodic Fast Radio Bursts from ULX-like Binaries

The discovery of periodicity in the arrival times of the fast radio bursts (FRB) from two repeating sources poses a potential challenge to oft-studied magnetar scenarios. However, models which postulate that FRB emission results from relativistic magnetized shocks, or magnetic reconnection in a striped outflow, are not necessarily specific to magnetar engines, instead requiring only the impulsive injection of relativistic energy into a dense magnetized medium. Motivated thus, we outline a new scenario in which FRBs are powered by short-lived relativistic outflows (“flares”) from accreting black hole or neutron star systems, which propagate into the cavity of the pre-existing (“quiescent”) jet. In order to reproduce FRB luminosities and rates, we are driven to consider binaries of stellar-mass compact objects undergoing super-Eddington mass transfer, similar to those which characterize ultraluminous X-ray (ULX) sources. Indeed, the host galaxies of FRBs, and their spatial offsets within their hosts, show broad similarities to those of ULXs. Periodicity on timescales of days to years could be attributed to precession (e.g., Lens-Thirring) of the polar accretion funnel, along which the FRB emission is geometrically and relativistically beamed, which sweeps across the observer line of sight. Accounting for the most luminous FRBs via accretion power may require a population of binaries undergoing brief-lived phases of unstable (dynamical timescale) mass transfer. This could lead to secular evolution in the burst properties of some repeating FRB sources on timescales as short as months to years, followed by a transient optical/IR counterpart akin to a luminous red nova or dusty common envelope transient. We encourage targeted FRB searches of known ULX sources.