Spitzer Space Telescope spectra of post-AGB stars in the large magellanic Cloud - polycyclic aromatic hydrocarbons at low metallicities
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This paper reports variations of polycyclic aromatic hydrocarbons (PAHs) features that were found in Spitzer Space Telescope spectra of carbon-rich post-asymptotic giant branch (post-AGB) stars in the Large Magellanic Cloud (LMC). The paper consists of two parts. The first part describes our Spitzer spectral observing programme of 24 stars including post-AGB candidates. The latter half of this paper presents the analysis of PAH features in 20 carbon-rich post-AGB stars in the LMC, assembled from the Spitzer archive as well as from our own programme.We found that five post-AGB stars showed a broad feature with a peak at 7.7 μm, that had not been classified before. Further, the 10-13 μm PAH spectra were classified into four classes, one of which has three broad peaks at 11.3, 12.3 and 13.3 μm rather than two distinct sharp peaks at 11.3 and 12.7 μm, as commonly found in HII regions. Our studies suggest that PAHs are gradually processed while the central stars evolve from post-AGB phase to planetary nebulae, changing their composition before PAHs are incorporated into the interstellar medium. Although some metallicity dependence of PAH spectra exists, the evolutionary state of an object is more significant than its metallicity in determining the spectral characteristics of PAHs for LMC and Galactic post-AGB stars.
Matsuura , M , Bernard-Salas , J , Lloyd Evans , T H H , Volk , K M , Hrivnak , B J , Sloan , G C , Chu , Y-H , Gruendl , R , Kraemer , K E , Peeters , E , Szczerba , R , Wood , P R , Zijlstra , A A , Hony , S , Ita , Y , Kamath , D , Lagadec , E , Parker , Q A , Reid , W A , Shimonishi , T , Winckel , H V , Woods , P M , Kemper , F , Meixner , M , Otsuka , M , Sahai , R , Sargent , B A , Hora , J L & McDonald , I 2014 , ' Spitzer Space Telescope spectra of post-AGB stars in the large magellanic Cloud - polycyclic aromatic hydrocarbons at low metallicities ' Monthly Notices of the Royal Astronomical Society , vol 439 , no. 2 , pp. 1472-1493 . DOI: 10.1093/mnras/stt2495
Monthly Notices of the Royal Astronomical Society
© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
RSz acknowledges support from Marie Curie Actions IRSES (project No. 269193) of EU and from Polish NCN grant 2011/01/B/ST9/02031. FK acknowledges financial support from the National Science Council under grant number NSC100-2112-M-001-023-MY3.
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