Astrophysical Significance of Asymptotic Giant Branch Stellar Wind Energies Recorded in Meteoritic SiC Grains

Abstract

Using model calculations for ion implantation into spherical grains in free space, we have identified two noble gas components implanted with high and low energies into presolar SiC grains isolated from the Murchison meteorite. The low-energy component seems to be associated with the stellar winds of expanding asymptotic giant branch (AGB) stars during the main stage of their evolution. In contrast, the high-energy component was probably generated during the late, thermally pulsing peak of AGB evolution and was implanted into SiC grains as a high-speed, post-AGB wind during the planetary nebula formation stage. If true, this is the first time that such a planetary nebular component has been identified in the laboratory and provides astrophysics with a new arena of research possibilities. Possible involvement of chemically active elements in the implantation events established for noble gases is also discussed. Although we have concentrated on evidence provided by the implantation of noble gases, we also extend the discussions to chemically active elements such as Ba and Sr.