  More than 100 rotating radio transients (RRATs) have been discovered since
2006. However, it is unclear whether RRATs radiate in the nulling states. PSR
J0628+0909 has been classified as an RRAT. In this paper, we study the single
pulses and integrated pulse profile of PSR J0628+0909 to check whether we can
detect pulsed radio emission in the nulling states. We also aim to study the
polarization of the RRAT and its relationship to the general pulsar population.
We used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to
observe PSR J0628+0909 in the frequency range from 1.0 to 1.5 GHz. We searched
for strong single pulses and looked for pulsed emission in the RRAT nulling
states. Polarisation profiles, the single-pulse energy distribution, and
waiting-time statistics were measured. The Faraday rotation measure and
dispersion measure values are updated with the current observation. The
single-pulse polarisation behaviours show great diversity, similar to the case
of pulsars. Based on the integrated pulse profile and single-pulse energy
statistics, we argue that continuous pulsar-like emission exists in addition to
the transient-like burst emission for PSR J0628+0909. We find that the pulse
waiting time is not correlated with the pulse energy and conclude that the
strong transient emission of RRAT is not generated by the energy store-release
mechanism.
