Subsecond Periodic Fast Radio Bursts from Tidally Induced Starquakes near Black Hole–Neutron Star/Binary Neutron Star Coalescence

Abstract More than 800 fast radio bursts (FRBs) have been observed, including some FRBs with unusual properties. Notably, in 2022, the CHIME/FRB Collaboration reported three FRBs exhibiting subsecond periodic/quasiperiodic structures, although FRB 20191221A has recently been reclassified to originate from a galactic pulsar rather than a genuine FRB. In this paper, we propose a novel scenario to account for this class of FRBs with very short subsecond quasiperiodicity. When a neutron star (NS) follows an elliptical orbit around a stellar-mass black hole or another NS near coalescence, its crust may fracture due to direct tidal force from its companion and magnetic stress from the nonuniform magnetic field within, triggering starquake-induced FRBs. The subsecond period in the FRB is explained by the orbital period. We apply our model to current observations and explain the periodic property in FRB 20210206A and FRB 20210213A from CHIME using the appropriate model parameters. The strong magnetic field required by the fitting results of these two FRBs suggests that their central engine is a magnetar.