Decoding the message from meteoritic stardust silicon carbide grains

Karen M. Lewis, Maria Lugaro, Brad K. Gibson, Kate Pilkington

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Abstract

SiC mainstream grains are presolar grains believed to form in the envelopes of carbon rich asymptotic giant branch (AGB) stars with masses between 1.5 and 3 solar masses. These grains represent a conundrum as the 29Si and 30Si abundances indicate that they formed in stars of super-solar metallicity, before the solar system formed. To shed light on this problem, we use silicon isotopic abundances to derive an age-metallicity relation for the stars believed to have produced the SiC mainstream grains. For 2732 mainstream SiC grains listed in the Presolar Grain Database, we use the 29Si abundances with the latest galactic chemical evolution (GCE) models to derive [Fe/H], and 30Si abundances along with the models of Zinner et al. (2006) to determine an approximate birth age for the parent AGB star. Comparing our age-metallicity relation with observational relationships derived for nearby stars, we find that the spread of [Fe/H] is in agreement, but the mean [Fe/H] in our relation is higher by 0.2 dex. We propose that this difference is because stars with higher [Fe/H] produce more dust and thus are over-represented in our age metallicity diagram, a finding consistent with previous published works. This result offers a solution for the long-standing problem of silicon in Stardust SiC grains, confirms the necessity of coupling chemistry and dynamics in simulations of the chemical evolution of our Galaxy, and constrains the modelling of dust condensation in stellar winds as a function of the metallicity.

Original languageEnglish
Title of host publicationOrigin of Matter and Evolution of Galaxies 2013 - Proceedings of the 12th International Symposium on Origin of Matter and Evolution of Galaxies, OMEG 2013
PublisherAmerican Institute of Physics
Pages301-306
Number of pages6
Volume1594
ISBN (Print)9780735412286
DOIs
Publication statusPublished - 2014
Event12th International Symposium on Origin of Matter and Evolution of Galaxies, OMEG 2013 - Tsukuba, Japan
Duration: 18 Nov 201321 Nov 2013

Conference

Conference12th International Symposium on Origin of Matter and Evolution of Galaxies, OMEG 2013
CountryJapan
CityTsukuba
Period18/11/1321/11/13

Keywords

  • dust
  • extinction - meteorites
  • meteoroids -Galaxy: abundances - stars: AGB and post-AGB
  • meteors

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