A Candidate Period of 4.605 Days for FRB 20121102A and One Possible Implication of Its Origin

A firm establishment of the presence or the lack of periodicity in repeating fast radio bursts is crucial for determining their origins. Here, we compile 1145 radio bursts of FRB 20121102A with fluence larger than 0.15 Jy ms from observations using the Five-hundred-meter Aperture Spherical radio Telescope, the Arecibo Observatory, the Green Bank Telescope, the Effelsberg Telescope, the MeerKAT Telescope, the Lovell Telescope, the Deep Space Network 70 m radio telescopes, the Very Large Array, and the Westerbork Synthesis Radio Telescope, spanning the time interval of MJD 57175-58776. A quasi-period of 157.1-4.8+5.2 days and a candidate quasi-period of 4.605-0.010+0.003 days are found through the phase-folding probability binomial analysis. The former is consistent with previous findings and the latter is new. The 4.605 day periodicity is more obvious in high-energy bursts with fluence larger than 1 x 1038 erg. The presence of these (candidate) quasi-periods, together with the corresponding width of burst accumulation in the phase space, are consistent with the bursts originating from a binary degenerate star system with a close-by planet around the primary neutron star.