2020ApJ...905L...5U

An origin of the optical/ultraviolet (UV) radiation from tidal disruption events (TDEs) has recently been discussed for different scenarios, but observational support is generally lacking. In this Letter, we test the applicability of the "wind-driven model" for a sample of UV/optical TDEs. With the model, we aim to derive the physical properties of the optical/UV TDEs, such as mass-loss rates and characteristic radii. The model assumes optically thick continuous outflows like stellar winds, and one key question arises: how is the wind-launched radius connected to physical processes in TDEs? Here we propose one possibility: through a comparison between the escape velocities estimated from their black hole masses and the wind velocities estimated from observed line widths, the outflow is launched from the self-interaction radius (R_SI) where the stellar debris stretched by the tidal force intersects. We show that the escape velocities at R_SI are roughly consistent with the wind velocities. By applying the model to a sample of optical/UV TDE candidates, we find that explosive mass ejections (>=10 M_☉ yr^–1) from R_SI (∼10¹⁴ cm) can explain the observed properties of TDEs around peak luminosity. We also apply the same framework to a peculiar transient, AT2018cow. This model suggests that AT2018cow is likely a TDE induced by an intermediate-mass black hole (M_BH ∼ 10⁴ M_☉).