http://arxiv.org/abs/1510.04286
Double-degenerate (DD) mergers of carbon-oxygen (CO) white dwarfs have recently emerged as a leading candidate for normal Type Ia supernovae (SNe Ia). However, many outstanding questions surround DD mergers, including the characteristics of their light curves and spectra. We have recently identified a spiral instability in the post-merger phase of DD mergers, and demonstrated that this instability self-consistently leads to detonation in some cases. We call this the spiral merger SN Ia model. Here, we utilize the \supernu\ radiative transfer software to calculate 3D synthetic light curves and spectra of the spiral merger simulation with a system mass of 2.1 $M_\odot$ of Kashyap et al. 2015. Because of their large system masses, both violent and spiral merger light curves are slowly declining. The spiral merger resembles very slowly-declining SNe Ia, including SN 2001ay, and provides a more natural explanation for its observed properties than other SN Ia explosion models. Previous synthetic light curves and spectra of violent DD mergers demonstrate a strong dependence on viewing angle, in conflict with observations. We demonstrate here that light curves and spectra of the spiral merger are less sensitive to the viewing angle than violent mergers, in closer agreement with observation. We find that the spatial distribution of $^{56}$Ni and intermediate-mass elements follows a characteristic hourglass shape. We discuss the implications of the asymmetric distribution of $^{56}$Ni for the early-time gamma-ray observations of $^{56}$Ni from SN 2014J. We suggest that DD mergers that agree with light curves and spectra of normal SNe Ia will likely require a lower system mass.
D. Rossum, R. Kashyap, R. Fisher, et. al.
Fri, 16 Oct 15
23/67
Comments: Submitted to ApJ
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