TY - JOUR
T1 - Spitzer Space Telescope spectra of post-AGB stars in the large magellanic Cloud - polycyclic aromatic hydrocarbons at low metallicities
AU - Matsuura, M.
AU - Bernard-Salas, J.
AU - Lloyd Evans, Thomas Harry Hope
AU - Volk, K.M.
AU - Hrivnak, B.J.
AU - Sloan, G.C.
AU - Chu, Y.-H.
AU - Gruendl, R.
AU - Kraemer, K.E.
AU - Peeters, E.
AU - Szczerba, R.
AU - Wood, P.R.
AU - Zijlstra, A.A.
AU - Hony, S.
AU - Ita, Y.
AU - Kamath, D.
AU - Lagadec, E.
AU - Parker, Q.A.
AU - Reid, W.A.
AU - Shimonishi, T.
AU - Winckel, H.V.
AU - Woods, P.M.
AU - Kemper, F.
AU - Meixner, M.
AU - Otsuka, M.
AU - Sahai, R.
AU - Sargent, B.A.
AU - Hora, J.L.
AU - McDonald, I.
N1 - 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.
PY - 2014/4/1
Y1 - 2014/4/1
N2 - 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.
AB - 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.
KW - Stars: AGB and post-AGB
KW - Circumstellar matter
KW - Galaxies: individual: Large Magellanic Cloud
KW - Infrared: stars
U2 - 10.1093/mnras/stt2495
DO - 10.1093/mnras/stt2495
M3 - Article
AN - SCOPUS:84897087849
SN - 0035-8711
VL - 439
SP - 1472
EP - 1493
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -