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2014MNRAS.440..631J - Mon. Not. R. Astron. Soc., 440, 631-651 (2014/May-1)

Modelling the alumina abundance of oxygen-rich evolved stars in the Large Magellanic Cloud.


Abstract (from CDS):

In order to determine the composition of the dust in the circumstellar envelopes of oxygen-rich asymptotic giant branch (AGB) stars, we have computed a grid of modust radiative-transfer models for a range of dust compositions, mass-loss rates, dust-shell inner radii and stellar parameters. We compare the resulting colours with the observed oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC) sample, finding good overall agreement for stars with a mid-infrared excess. We use these models to fit a sample of 37 O-rich AGB stars in the LMC with optically thin circumstellar envelopes, for which 5-35 µm Spitzer infrared spectrograph (IRS) spectra and broad-band photometry from the optical to the mid-infrared are available. From the modelling, we find mass-loss rates in the range ∼ 8x10–8-5x10–6M/yr, and we show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron, provides a good fit to the observed spectra. Furthermore, we show from dust models that the AKARI [11]-[15] versus [3.2]-[7] colour-colour diagram is able to determine the fractional abundance of alumina in O-rich AGB stars.

Abstract Copyright: © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2014)

Journal keyword(s): radiative transfer - stars: AGB and post-AGB - circumstellar matter - dust, extinction - Magellanic Clouds - infrared: stars

VizieR on-line data: <Available at CDS (J/MNRAS/440/631): tablea1.dat>

Simbad objects: 151

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