Radio Properties of Rotating Radio Transients I: searches for
  periodicities and randomness in pulse arrival times
  We have analysed the long- and short-term time dependence of the pulse
arrival times and the pulse detection rates for eight Rotating Radio Transient
(RRAT) sources from the Parkes Multi-beam Pulsar Survey (PMPS). We find
significant periodicities in the individual pulse arrival times from six RRATs.
These periodicities range from 30 minutes to 2100 days and from one to 16
independent (i.e. non-harmonically related) periodicities are detected for each
RRAT. In addition, we find that pulse emission is a random (i.e. Poisson)
process on short (hour-long) time scales but that most of the objects exhibit
longer term (months-years) non-random behaviour. We find that PSRs J1819-1458
and J1317-5759 emit more doublets (two consecutive pulses) and triplets (three
consecutive pulses) than is expected in random pulse distributions. No evidence
for such an excess is found for the other RRATs. There are several different
models for RRAT emission depending on both extrinsic and intrinsic factors
which are consistent with these properties.
