Circumstellar magnetite from the LAP 031117 CO3.0 chondrite

Thomas J. Zega, Pierre Haenecour, Christine Floss, Rhonda M. Stroud

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

We report the first microstructural confirmation of circumstellar magnetite, identified in a petrographic thin section of the LaPaz Icefield 031117 CO3.0 chondrite. The O-isotopic composition of the grain indicates an origin in a low-mass (∼2.2 Mo.), approximately solar metallicity red/asymptotic giant branch (RGB/AGB) star undergoing first dredge-up. The magnetite is a single crystal measuring 750 × 670 nm, is free of defects, and is stoichiometric Fe3O4. We hypothesize that the magnetite formed via oxidation of previously condensed Fe dust within the circumstellar envelope of its progenitor star. Using an empirically derived rate constant for this reaction, we calculate that such oxidation could have occurred over timescales ranging from approximately ∼9000-500,000 years. This timescale is within the lifetime of estimates for dust condensation within RGB/AGB stars.

Original languageEnglish (US)
Article number55
JournalAstrophysical Journal
Volume808
Issue number1
DOIs
StatePublished - Jul 20 2015

Keywords

  • circumstellar matter
  • stars: AGB and post-AGB
  • stars: evolution
  • stars: formation
  • stars: fundamental parameters
  • stars: winds outflows

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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