Different Origins for the Line-emitting and Photospheric Components in Tidal Disruption Events: A Case for ASASSN-14ae

Abstract Tidal disruption events (TDEs) are believed to launch outflows that play a crucial role in producing optical emission lines. In this study, we investigate emission properties expected within the wind-driven outflow framework, in which an outflow is continuously injected from the central engine. We perform radiative transfer calculations to compute synthetic line properties and apply the model to the optical TDE ASASSN-14ae. We find that a two-component structure with a high density contrast, consisting of an optically thick inner layer and an optically thin outer layer, is required to simultaneously reproduce the observed photospheric and H α properties. The optically thin component exhibits a power-law temporal evolution in the mass-outflow rate and kinetic power, with the total ejected mass of ∼0.25 M ⊙ , indicating that it might originate in a super-Eddington accretion-disk-driven outflow. The optically thick component is responsible for the photospheric emission, and we argue that this component is more plausibly interpreted as a quasi-hydrostatic envelope rather than an outflow. Interestingly, the kinetic power of the optically thin component and the bolometric luminosity originating from the optically thick component are comparable, and they share the same temporal evolution. This finding indicates that these two components are energetically linked through an equipartition process—pointing to a scenario in which the accretion energy is first converted to the kinetic energy of the outflow, and then this energy is dissipated to the envelope through the outflow–envelope interaction before it emerges from the surface of the envelope.