Astron. Astrophys. 328, 331-338
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The chemical composition of IRAS 05341+0852:
a post-AGB F supergiant with 21 µm emission
B.E. Reddy1, M. Parthasarathy1,2, G. Gonzalez3,4, and E.J. Bakker3
1Indian Institute of Astrophysics, Bangalore - 560
2Observatoire Astronomique, de Strasbourg, 11 rue de l' Universite,
F-67000 Strasbourg, France
3Department of Astronomy and McDonald Observatory,
University of Texas, Austin, TX 78712, USA
4Present address: Astronomy Department, University of Washington,
Box 351580, Seattle, WA 98195-1580 USA
Received 22 April 1997 / Accepted 11 July 1997
An abundance analysis of the photosphere of the
F-type Post-AGB candidate IRAS 05341+0852 is presented.
The analysis of the spectra suggests that the atmospheric model: Teff=6500 K, log g=0.5,
=5 km s-1 and [M/H]=-1.0, best represents the photosphere of the star.
that the star is metal-poor ([Fe/H]=-0.9) and carbon-rich (C/O1.9).
Lithium, carbon, nitrogen, oxygen, aluminum and silicon
are found to be
Most importantly this star has large
overabundance of s-process elements which are as follows:
[Y/Fe]=1.6, [Ba/Fe]=2.2, [La/Fe]=2.9, [Ce/Fe]=1.6, [Pr/Fe]=1.8,
[Nd/Fe]=2.0, and [Sm/Fe]=1.7.
These s-process enhancements are of similar magnitude to those seen in FG Sge.
The enhancement of Li and Al are expected due to Hot Bottom
Burning (HBB), in massive AGB stars.
However, the low metallicity, heliocentric
radial velocity (vr=25 km s-1), and the high Galactic
latitude (b=-12o) suggest that IRAS 05341+0852 is a low-mass star.
Also the [S/Fe]=0.2 indicates that the
low Fe abundance is intrinsic and is not due to fractionation.
The significant overabundance of lithium (log ) and aluminum
([Al/Fe]=1.4) in this star is a puzzle.
Furthermore we have detected the C2 Phillips and CN Red bands in
absorption. We find rotational temperatures, column densities, and
expansion velocities which show that these lines are formed in the
detached circumstellar dust shell (the AGB ejecta) and we find
an expansion velocity of the AGB ejecta of
Key words: stars: abundances - stars: carbon-stars; post-AGB
stars; circumstellar matter - stars: individual: IRAS 05341+0852
© European Southern Observatory (ESO) 1997
Online publication: October 30, 1997
Last change: March 24, 1998