Contributed Talk

The 6.9-micron and 15.8-micron Features in Magellanic Cloud Post-AGB Stars

Mikako Matsuura (University College London)

The 6.9- and 15.8-micron features had been found in just over ten Galactic post-AGB stars, their characters are not well studied. It has been proposed that the 6.9-micron feature is due to aliphatic carbon, and 15.8-micron feature is due to PAHs. We have studied Spitzer Space Spectra of post-AGB stars in the Large Magellanic Cloud (LMC). We found these features commonly in post-AGB stars in the Magellanic Clouds, and also they are very strong. The LMC initial metallicity is about half of the solar metallicity. AGB stars synthesise carbon in their stellar interior, but the low initial metallicity results in a higher carbon to oxygen ratio, as the oxygen abundance is low in the LMC. Thus, we observe these features more commonly in the low metallicity galaxies, than the Milky Way.

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