Chemical composition of post-AGB star candidates. (arXiv:1901.05866v1 [astro-ph.SR])

Chemical composition of post-AGB star candidates. (arXiv:1901.05866v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Molina_R/0/1/0/all/0/1">R. E. Molina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pereira_C/0/1/0/all/0/1">C. B. Pereira</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ferro_A/0/1/0/all/0/1">A. Arellano Ferro</a>

We present a high resolution detailed abundance analysis for a sample of six
post-AGB candidate stars, five of them had not been studied spectroscopically
in the optical region. All the analyzed objects are IRAS sources identified as
possible post-AGB on the two-colours IRAS diagram. We find three objects with
clear signs of evolved stars; IRAS 05338-3051 shows abundances similar to the
RV Tauri V453 Oph; the lower-luminosity stars IRAS 18025 – 3906 is O-rich
without s-process enrichment and IRAS 18386 – 1253 shows a moderate selective
depletion of refractory elements generally seen in post-AGB stars, which show
mid-IR excess; they may be evolved post-RGB objects, in which case these would
be the first Galactic counterparts of post-RGB objects observed in the Large
and Small Magellanic Clouds (Kamath et al. 2014, 2015). On the other hand, IRAS
02528 + 4350 seems to be a moderately metal-poor young object and IRAS 20259 +
4206 also seems to be a young object showing carbon deficiency; however, an
analysis with better spectra might be in order to clarify its evolutionary
state. Finally, our abundances calculations for the binary post-AGB star IRAS
17279 – 1119 are found in good agreement with those of De Smedt et al. (2016).

We present a high resolution detailed abundance analysis for a sample of six
post-AGB candidate stars, five of them had not been studied spectroscopically
in the optical region. All the analyzed objects are IRAS sources identified as
possible post-AGB on the two-colours IRAS diagram. We find three objects with
clear signs of evolved stars; IRAS 05338-3051 shows abundances similar to the
RV Tauri V453 Oph; the lower-luminosity stars IRAS 18025 – 3906 is O-rich
without s-process enrichment and IRAS 18386 – 1253 shows a moderate selective
depletion of refractory elements generally seen in post-AGB stars, which show
mid-IR excess; they may be evolved post-RGB objects, in which case these would
be the first Galactic counterparts of post-RGB objects observed in the Large
and Small Magellanic Clouds (Kamath et al. 2014, 2015). On the other hand, IRAS
02528 + 4350 seems to be a moderately metal-poor young object and IRAS 20259 +
4206 also seems to be a young object showing carbon deficiency; however, an
analysis with better spectra might be in order to clarify its evolutionary
state. Finally, our abundances calculations for the binary post-AGB star IRAS
17279 – 1119 are found in good agreement with those of De Smedt et al. (2016).

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