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., $10^3~{\rm sec} \lesssim t_{\rm exp} \lesssim 1~{\rm day}$). The main source of the expelled mass is a disk-wind, or jets that are launched by the accretion disk around the more massive WD during the viscous phase of the merger. This disk-originated matter (DOM) will be shocked and heated by the SN ejecta from an explosion, leading to additional radiation in the early lightcurve. 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. 
Naveh Levanon, Noam Soker (Technion, Israel) and Enrique   Garc\'ia-Berro (Universitat Polit\`ecnica de Catalunya)
astro-ph.SR astro-ph.HE