Complementary Trace Element Abundances in Meteoritic S[CLC]i[/CLC]C Grains and Carbon Star Atmospheres

Abstract

Equilibrium condensation calculations successfully explain the complementary trace element abundance patterns observed in carbon star atmospheres and circumstellar SiC grains found in meteorites. Fractional trace element condensation into SiC depletes the gas in refractory trace elements, while more volatile elements remain in the gas. The observed complementary patterns imply that dust forms relatively close to the star, possibly during the minimum light phase in stellar variability cycles. Once the gas falls back onto the star during stellar contraction, photospheric abundances become relatively enriched in more volatile elements. The complementary trace element abundances link circumstellar SiC grains from meteorites to carbon star atmospheres. © 1997. The American Astronomical Society. All rights reserved.