Type Iax supernovae as a source of iron-rich silicate dust

Abstract

We model the formation of dust in the ejecta of Type Iax supernovae (SNe), which is a low-luminosity subclass of Type Ia SNe. A non-equilibrium chemical kinetic approach is adopted to trace the synthesis of molecules, molecular clusters, and dust grains in the ejecta of thermonuclear SNe. We find that Type Iax SNe provide conditions conducive to the formation of several O-rich dust species in the ejecta. Particularly, iron-rich silicates of chemical type FeSiO3, Fe2SiO4, and MgFeSiO4 are found to form in abundance, suggesting that the ejecta of low-luminosity thermonuclear SNe can be a site where a large fraction of iron is locked up in dust, unlike other stellar sources. The final mass of dust formed in the ejecta ranges between 10^{-5} and 10^{-4} Msun, where most of the dust forms between 1000 and 2000 days post-explosion. Apart from Fe-rich silicates, Mg-silicates, and silicon carbide are also formed in the ejecta of Type Iax SNe. When compared to the dust budget of typical Type Ia SNe, we find that the expected dust-to-ejecta mass ratio is 1 or 2 orders of magnitude larger in Type Iax SNe. We conclude that the ejecta of typical Type Ia SNe form a negligible amount of dust, in agreement with observation, while the low-luminosity subclass Type Iax SNe are potential producers of iron-rich silicates.