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New identifications for blue objects towards the Galactic center: post-AGB stars, Be/disk stars and others *
K.A. Venn 1, 2, 3,
S.J. Smartt 4, 5,
D.J. Lennon 2 and
P.L. Dufton 4
Received 16 February 1998 / Accepted 19 March 1998
As part of a programme to investigate spatial variations in the Galactic chemical composition, we have been searching for normal B-type stars and A-type supergiants near the Galactic center. During this search we have found eleven peculiar stars, and in some cases performed detailed abundance analyses of them which suggest that they may be at a post-AGB evolutionary stage.
The A-type post-AGB candidates show [Fe/H]=-1.0 to -2.0, and [O/Fe] +1.4, typical of the post-AGB abundance patterns discussed in the literature. One star, LS 3591 (=SAO 243756), has also been examined recently by Oudmaijer (1996); its spectrum appears to be changing very rapidly, which may indicate erratic mass loss or the incipient formation of a planetary nebula.
A B-type post-AGB candidate, LS 4950, has a similar spectrum to a well studied post-AGB star, LSIV -12 111. However, an examination of the line strengths and elemental abundances of LS 4950 show that it is peculiar for both a Population II, post-AGB, B-type star and for a normal, Population I, B-type supergiant. Two other B-type stars, LS 4825 and LS 5112, are either post-AGB stars near the Galactic center or normal B-type supergiants lying well beyond the Galactic center. In addition, several Be-type stars have been newly (or more clearly) identified from our spectra.
Key words: stars: abundances stars: emission-line, Be stars: fundamental parameters stars: AGB and post-AGB stars: supergiants Galaxy: centre
Send offprint requests to: K.A. Venn, Macalester College, Department of Physics and Astronomy, 1600 Grand Ave., St. Paul, MN, 55105, USA
© European Southern Observatory (ESO) 1998
Online publication: June 2, 1998