Repeating FRB 121102: Eight-year Fermi-LAT Upper Limits and Implications

Abstract

The repeating fast radio burst (FRB) source that produced FRB 121102 was recently localized in a star-forming galaxy at z  = 0.193, which is associated with an extended radio source at the burst location. One possibility is that the repeating FRBs are produced by a new-born magnetar, which also powers the radio nebula. If so, the magnetar may produce γ -ray emission due to magnetic dipolar spin-down. The luminosity depends on the magnetar spin parameters and age. We process the eight-year Fermi -LAT data at the position of FRB 121102 and place an energy flux upper limit of in time bins with six-month intervals, and an accumulated energy flux upper limit of over the eight-year span. The corresponding γ -ray luminosity upper limits are and for the time-resolved and time-integrated analyses, respectively. We discuss the implications of these limits on the young magnetar model.