SN 2010lp---a Type Ia supernova from a violent merger of two carbon--oxygen White Dwarfs

SN 2010lp is a subluminous Type Ia supernova (SN Ia) with slowly-evolving lightcurves. Moreover, it is the only subluminous SN Ia observed so far that shows narrow emission lines of OI in late-time spectra, indicating unburned oxygen close to the centre of the ejecta. Most explosion models for SNe Ia cannot explain the narrow OI emission. Here, we present hydrodynamic explosion and radiative transfer calculations showing that the violent merger of two carbon-oxygen white dwarfs of 0.9 and 0.76 solar masses, respectively, adequately reproduces the early-time observables of SN 2010lp. Moreover, our model predicts oxygen close to the centre of the explosion ejecta, a pre-requisite for narrow OI emission in nebular spectra as observed in SN 2010lp.