Aggregation of SiC-X Grains in Supernova Ejecta

TL;DR

This paper models the formation of silicon carbide (SiC-X) grain aggregates in supernova ejecta, explaining their isotopic homogeneity and aggregation process through shock-induced condensation and gas drag effects.

Contribution

It introduces a new model linking supernova shock dynamics to the formation and aggregation of SiC-X grains, explaining their isotopic uniformity.

Findings

SiC-X grains form within a dense shell created by a reverse shock.

Gas drag limits the travel distance of grains, influencing aggregation.

Aggregates originate from localized condensation regions.

Abstract

We present a model for the formation of silicon carbide aggregates within the expanding and cooling supernova remnant. Many SiC-X grains have been found to be aggregates of smaller crystals which are isotopically homogenous. The initial condensation of SiC in the ejecta occurs within a interior dense shell of material which is created by a reverse shock which rebounds from the core-envelope interface. A subsequent reverse shock accelerates the grains forward, but the gas drag from the ejecta on the rapidly moving particles limits their travel distance. By observing the effects of gas drag on the travel distance of grains, we propose that supernova grain aggregates form from material that condensed in a highly localized region, which satisfies the observational evidence of isotopic homogeneity in SiC-X grains.