A Wind-Driven Model: Application to Peculiar Transients AT2018cow and iPTF14hls

We propose a wind-driven model for peculiar transients, and apply the model to AT2018cow and iPTF14hls. In the wind-driven model, we assume that a continuous outflow like a stellar wind is injected from a central system. While these transients have different observational properties, this model can explain their photometric properties which are not reproduced by a supernova-like instantaneous explosion. Furthermore, the model predicts characteristic spectral features and evolution, which are well in line with those of AT2018cow and iPTF14hls. Despite the different observational properties, the wind model shows that they have some common features; the large mass-loss rates (up to $\sim 20M_{\odot}{\rm ~yr^{-1}}$ for AT2018cow and $\sim 75M_{\odot}{\rm ~yr^{-1}}$ for iPTF14hls), and the characteristic radii of $\sim 10^{13}{\rm ~cm}$ for the launch of the wind. It would indicate that both may be related to events involving a red super giant (RSG), in which the RSG envelope is rapidly ejected by an event at a stellar core scale. On the other hand, the main differences are the kinetic energies, the total ejected mass, and time scales. We then suggest that iPTF14hls may represent a dynamical common-envelope evolution induced by a massive binary system ($\sim 120M_{\odot}+100M_{\odot}$). AT2018cow may be either a tidal disruption event of a low-mass RSG by a black hole (BH), or a BH-forming failed supernova.