Molecular nucleation theory of dust formation in core-collapse supernovae applied to SN 1987A

Alan Sluder, Milos Milosavljevic, Michael H. Montgomery

Published 2016-12-29Version 1

We model dust formation in a core collapse supernova explosion like that of SN 1987A. In treating the gas-phase formation of dust grain nuclei as a chemical process, our model borrows from and improves upon the recent progress toward modeling dust formation. We compute the synthesis of fourteen species of dust grains in supernova ejecta generated with a stellar evolutionary and explosive nucleosynthesis calculation designed to approximate the parameters of SN 1987A. We explicitly integrate a non-equilibrium network of the chemical reactions contributing to the production of each species' condensation nuclei and follow the growth of condensation nuclei into grains via accretion and coagulation. We include the effects of radioactive decay of Co56, Co57, Ti44, and Na22 on the chemistry and thermodynamics of the ejecta, and of grain electric charge on grain growth. The grain temperature is used to calculate the evaporation rate. The van der Waals force between grains is included in the coagulation model. In addition to evaporation, we include He+, Ne+, Ar+, and O weathering as grain destruction processes. We use our dust synthesis model in combination with a crude model for anisotropic Ni56 dredge-up into the core ejecta, which produces the so-called "nickel bubbles", to compute the total dust mass and molecular-species-specific grain size distribution. We find a total dust mass between 0.4 and 0.73 M_sun, depending on the density in the perturbations caused by the nickel bubbles. The dominant grain species produced, from highest mass to lowest mass, are: magnesia, silicon, forsterite, iron sulfide, carbon, silicon dioxide, alumina, and iron. The combined grain size distribution is a power law dN/da~a^{-4.39}, steeper than the observationally inferred dN/da~a^{-3.5}. Early ejecta compaction by expanding radioactive Ni56 bubbles strongly enhances dust synthesis.