Constraining the double-degenerate scenario for Type Ia supernovae from merger ejected matter

We follow the mass expelled during the WD–WD merger process in a particular case of the double-degenerate (DD) scenario for Type Ia supernovae (SNe Ia), and find that the interaction of the SN ejecta with the resulting wind affects the early (first day) light-curve in a way that may be in conflict with some SN Ia observations, if the detonation occurs shortly after the merger, i.e. (103 s ≲ texp ≲ 1 d). The main source of the expelled mass is a disc-wind, or jets that are launched by the accretion disc around the more massive white dwarf (WD) during the viscous phase of the merger. This disc-originated matter will be shocked and heated by the SN ejecta from an explosion, leading to additional radiation in the early light-curve. This enhanced early radiation could then be interpreted as an explosion originating from a progenitor having an inferred radius of one solar radius or more, in conflict with observations of SN 2011fe.