The Magnetar Model and the Ejecta--Circumstellar-Matter Interaction Model for 31 Luminous, Rapidly Evolving Optical Transients.

We study 31 luminous, rapidly evolving optical transients (REOTs), and use the magnetar model and the ejecta--circumstellar-matter (CSM) interaction (CSI) model to fit their multiband light curves. We find that 28 events can be fitted by the magnetar model. and the derived masses ($\sim0.05$--5.58\,M$_\odot$) are consistent with that of stripped and ultrastripped core-collapse supernovae (CCSNe). On the other hand, the CSI model can fit 25 events; the derived ejecta masses are $\sim 3$--30\,M$_\odot$, consistent with that of SNe~Ibn. The results, together with the fact that many luminous REOTs have been confirmed to be luminous SNe~IIb/Ib/c or Ibn/IIn, suggest that at least a fraction of luminous REOTs spectroscopically unclassified might be rapidly evolving SNe~Ib/Ic or Ibn. Three events in the sample cannot be explained by the two models we use. We expect that future intense photometry, spectroscopic classifications, and systematic light-curve modeling of luminous REOTs will shed more light on their nature.