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The chemical composition of IRAS 05341+0852: a post-AGB F supergiant with 21 μm emission

Published online by Cambridge University Press:  25 May 2016

B. E. Reddy ,
M. Parthasarathy ,
G. Gonzalez  and
E. J. Bakker
B. E. Reddy
Affiliation:
1Indian Institute of Astrophysics, Bangalore
M. Parthasarathy
Affiliation:
1Indian Institute of Astrophysics, Bangalore 2Observatoire Astronomique, Strasbourg
G. Gonzalez
Affiliation:
3,4University of Texas, Austin
E. J. Bakker
Affiliation:
3,4University of Texas, Austin

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An abundance analysis of the photosphere of the F-type Post-AGB candidate IRAS 05341-+0852 is presented. It shows that the star is metal-poor ([Fe/H]=–1.0) and carbon-rich (C/0≈2.2). Carbon, nitrogen, oxygen, silicon, and possibly lithium and aluminum are found to be over abundant. Most importantly this star has large overabundance of s-process elements which are as follows: [Y/Fe]= 1.80, [Ba/Fe]= 2.58, [La/Fe]= 2.86, [Ce/Fe]= 2.95, [Pr/Fe]= 2.27, [Nd/Fe]= 1.97, and [Sm/Fe]= 0.86. The overabundances of s-process elements and carbon in IRAS 05341+0852 is direct evidence for the association of s-process enhancements with shell-flashes and dredge-up. These are likely responsible for the increase in C/O. The possible overabundance of Li ([Li/Fe]≤2.5) and Al ([Al/Fe]≤ 1.1) in IRAS 05341+0852 could indicate that there was Hot Bottom Burning (HBB), where the base of the convective envelope is hot enough for nucleosynthesis to occur (Lattanzio 1993). HBB has been suggested as the mechanism responsible for the production of Li in the Li-rich AGB stars discovered by Smith and Lambert (1989). In fact these are bright AGB stars which are oxygen-rich rather than carbon-rich. Recent calculations by Sackmann and Boothroyd (1992) showed that Li-rich and O-rich AGB stars are the result of HBB. In the HBB models temperatures of the order of 0.5–1 × 108 K are encountered at the base of the convective envelope (Blöcker and Schönberner 1991). This is hot enough for the reaction 25Mg(p,γ) 26 Al resulting in the production of Al.

Type
V. From AGB to Planetary Nebulae
Information
Symposium - International Astronomical Union , Volume 180: Planetary Nebulae , 1997 , pp. 366
Copyright
Copyright © Kluwer 1997 

References

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