Spectroscopic survey of field stars : A search for metal-poor stars

Abstract

We have undertaken a spectroscopic survey of field stars to fine metal-poor objects among them. Though the main objective of the survey is to find new metal-poor stars, stellar parameterization is carried out for all the sample stars so that the other categories of interesting objects like composite stars, weak or strong CN, CH stars etc. can also be identified. Observations are carried out using OMR spectrograph attached to VBT, Kavalur. The sample of candidate stars are chosen from prismatic survey of Beers and his collaborators covering a large part of the Galaxy. At the first phase of this project, the analysis of completed for a set of 19 relatively hot stars (Teff in 6000 to 8000K rage). The metallicities of the program stars are derived by synthesizing the spectrum in the wavelength range 4900 to 5400 Å for different metallicities and matching them with the observed spectra. This spectral region contains strong feature of Fe I at 5269 Å and one moderately strong Fe I blend at 5228 Å. These features were generally relied upon for Fe/H determination. More than half of the candidate stars were found to show (Fe/H) in -0.7 to -1.2 range. Two most metal-poor stars have (Fe/H) values of -1.3 and -1.8. It appears that metal-poor candidates suggested by Beers et al. from their prismatic survey has a very significant fraction of metal-poor stars. The significantly metal-poor stars found so far would be studied in detail using high resolution spectra to understand nucleosynthesis processes that might have occurred in early Galaxy.