Periodic Fast Radio Bursts from Young Neutron Stars
  Fast radio bursts (FRBs) are highly energetic radio pulses from cosmological
origins. Despite an abundance of detections, their nature remains elusive. At
least a subset of FRBs is expected to repeat, as the daily FRB rate surpasses
that of any known cataclysmic event, which has been confirmed by observations.
One of the proposed mechanisms to generate repeating FRBs is supergiant pulses
from young and highly spinning NSs, in which case FRBs could inherit the
periodicity of their parent NS. Here we examine the consequences of such a
population of periodic fast radio bursts (PFRBs). We calculate the rate and
lifetime of PFRB progenitors, and find that each newly born highly spinning NS
has to emit a number $N_{\rm PFRB}\sim 10^2$ of bursts during its active
lifetime of $\tau\sim 100$ years, after which it becomes too dim and crosses a
PFRB "death line" analogous to the pulsar one. We propose several tests of this
hypothesis. First, the period of PFRBs would increase over time, and their
luminosity would decrease, due to the NS spin-down. Second, PFRBs may show
modest amounts of rotation measure, given the lack of expelled matter from the
pulsar, as opposed to the magnetar-sourced FRBs proposed to explain the first
repeater FRB 121102. As an example, we study whether the second confirmed
repeater (FRB 180814) is a PFRB, given the preference for an inter-pulse
separation of 13 ms within its sub-bursts. We show that, if confirmed, this
period would place FRB 180814 in a different category as FRB 121102. We develop
tests that would identify---and characterize---the prospective population of
PFRBs.
