Bibcode
Parthasarathy, Mudumba; Sivarani, T.; Garcia-Lario, P.; Manchado, A.
Referencia bibliográfica
American Astronomical Society, 197th AAS Meeting, #60.05; Bulletin of the American Astronomical Society, Vol. 32, p.1503
Fecha de publicación:
12
2000
Número de citas
0
Número de citas referidas
0
Descripción
We have carried out an analysis of the high resolution optical spectra
of post-AGB candidates SAO 85766 (IRAS 18062+2410), SAO 34504 (IRAS
22272+5435), HD 187885 (IRAS 19500-1709), HD 331319 (IRAS 19475+3119),
HD 168625 (IRAS 18184-1623) and IRAS 10215-5916. All these objects have
far-infrared colors similar to planetary nebulae and proto- planetary
nebulae. Some of these are high galactic latitude stars. The spectrum of
SAO 85766 shows several permitted and forbidden emission lines and low
excitation nebular emission lines. We find the chemical composition of
SAO 85766 to be similar to that of high galatcic latitude hot post-AGB
stars with under abundance of carbon. The variations observed in the
spectrum of SAO 85766 indicates that it is rapidly evolving into a
planetary nebula ( similar to that SAO 244567 (Hen 1357)). SAO 34504 and
HD 187885 are post-AGB stars with 21 micron emission feature. We have
determined the atmospheric parameters and chemical composition of these
stars and confirm the over abundance of carbon and s-process elements.
These two stars appear to have evovled from the carbon star phase on the
AGB and are now carbon-rich post-AGB stars. The evolutionary status of
HD 331319, HD 168625 and IRAS 10215-5916 is not clear. They may be low
mass stars in post-AGB phase of evolution, or, they may be massive popI
supergiants. The chemical composition analysis of all the above
mentioned stars is presented.