  Tidal disruption events (TDEs) can uncover the quiescent black holes (BHs) at
the center of galaxies and also offer a promising method to study them. In a
partial TDE (PTDE), the BH's tidal force cannot fully disrupt the star, so the
stellar core survives and only a varied portion of the stellar mass is bound to
the BH and feeds it. We calculate the event rate of PTDEs and full TDEs
(FTDEs). In general, the event rate of PTDEs is higher than that of FTDEs,
especially for the larger BHs. And the detection rate of PTDEs is about dozens
per year by Zwicky Transient Factory (ZTF). During the circularization process
of the debris stream in PTDEs, no outflow can be launched due to the efficient
radiative diffusion. The circularized debris ring then experiences viscous
evolution and forms an accretion disk. We calculate the light curves of PTDEs
contributed by these two processes, along with their radiation temperature
evolution. The light curves have double peaks and the spectra peak in UV.
Without obscuration or reprocessing of the radiation by an outflow, PTDEs
provide a clean environment to study the circularization and transient disk
formation in TDEs.
