Orbital and Precession Periods in Repeating FRB 20121102A

Abstract

Abstract Li et al. reported a 4.605 days period in the repeating FRB 20121102A in addition to its previously reported 157 days modulation of activity. This note suggests that the shorter period is the orbital period of a mass-transferring star orbiting a black hole, possibly of intermediate mass, and that the 157 days period is the precession period of an accretion disk around the black hole. The mass-losing star must be evolved.