Repeating fast radio bursts produced by a strange star interacting with its planet in an eccentric orbit

Abstract

FRB 180916 is an important repeating fast radio burst (FRB) source. Interestingly, the activity of FRB 180916 shows a well-regulated behavior, with a period of 16.35 days. The bursts are found to occur in a duty circle of about 5 days in each period. In this study, we suggest that the bursts of FRB 180916 are produced by a strange star interacting with its planet. The planet moves in a highly eccentric orbit around its compact host, with the periastron only slightly beyond the tidal disruption radius. As a result, the planet will be partially disrupted every time it passes through the periastron. The stripped material from the planet will be accreted by the strange star, falling to the polar cap region along the magnetic field lines and accumulated there. It will finally lead to a local collapse when the crust at the polar region is overloaded, triggering an FRB. The observed 16.35 day period corresponds to the orbital motion of the planet, and the 5 day duty circle is explained as the duration of the partial disruption near the periastron. The energy released in each local collapse event can be as high as $\sim 10^{42}~\rm {erg}$, which is large enough to account for typical FRBs even if the radiation efficiency is extremely low.