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Accepted · first revision · record

Title: Origin of periodic activity windows in repeating FRB sources
Plain: Some repeating sources are active only in windows that recur every 16 or about 160 days, and the clock behind this is unknown.
Precise: FRB 20180916B shows activity windows with period $\sim 16.3\,\mathrm{days}$ and FRB 20121102A a candidate $\sim 160\,\mathrm{day}$ period. Identify the mechanism (binary orbit with a massive companion wind, free precession of a magnetar, or ultra-slow rotation) by predicting frequency-dependent window drift and phase-dependent dispersion measure, rotation measure and polarization. Answer: the mechanism consistent with all phase-resolved data.
Settled by: Phase-resolved monitoring of rotation measure, dispersion measure and polarization over many cycles, testing binary-orbit predictions against precession predictions of period drift.
Kind: well-posed
Answer type: identification
References: (empty)
Literature status: open
Status note: (empty)
Posed since: 2020