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The origin of presolar silica grains in AGB stars
Bose M., Floss C., Stadermann F. J., Stroud R. M., and Speck
A. (2010)
Lunar Planet. Sci. XLI, Abstract #1812.
ABSTRACT
Oxide and silicate grains have been identified by infrared
(IR) spectroscopy to be a major component of the dust shells in O-rich
Asymptotic Giant Branch (AGB) stars. Recently, such grains have also
been identified in the laboratory through investigations of meteoritic
presolar grains. Coordinated isotopic and elemental measurements of
these presolar grains can enhance our understanding of dust formation
processes in O-rich environments and also aid in the interpretation of
IR spectra.
The IR spectra of about half of all AGB stars exhibit a 13 µm
feature. A variety of phases have been proposed as its carrier
including SiO2 whose extinction spectra similarly show a 13 µm
peak. Here we report on two silica grains identified in the primitive
carbonaceous chondrite ALHA77307, and explore the possibility that
silica may be the carrier of the 13 µm feature associated with
evolved stars.
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