http://arxiv.org/abs/1910.12434
We use non-local thermal equilibrium (NLTE) radiative transport modeling to examine observational signatures of sub-Chandrasekhar mass double detonation explosions in the nebular phase. Results range from spectra that look like typical and sub-luminous Type Ia supernovae (SNe) for higher mass progenitors to spectra that look like Ca-rich transients for lower mass progenitors. This ignition mechanism produces an inherent relationship between emission features and the progenitor mass as the ratio of the nebular [CaII]/[FeIII] emission lines increases with decreasing white dwarf (WD) mass. Examining the [CaII]/[FeIII] nebular line ratio in a sample of observed SNe we find further evidence for the two distinct classes of SNe Ia identified in Polin et al. (2019) by their relationship between SiII velocity and B-band magnitude, both at time of peak brightness. This suggests that SNe Ia arise from more than one progenitor channel, and provides an empirical method for classifying events on based on their physical origin. Furthermore, we provide insight to the mysterious origin of Ca-rich transients as we show that only a small mass fraction of Ca (1%) is required to produce a nebular spectrum that cools primarily through forbidden [CaII] emission.
A. Polin, P. Nugent and D. Kasen
Tue, 29 Oct 19
78/78
Comments: 11 pages, 8 figures, submitted to ApJ on 27 October 2019