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Carbon Isotopic Abundances in the Red Giants of ω Centauri (NGC 5139)
12C and 13C abundances have been measured in 11bright giant members of the globular cluster ω Centauri viaobservations of the first-overtone CO bands near 2.3 μm. The stars inthis sample were selected to span a substantial fraction of the range ofiron abundances found in this cluster. In addition, the sample covers arange of [O/Fe], [Na/Fe], and [Al/Fe] abundance ratios derived inprevious studies. In all ω Cen giants the12C/13 C abundance ratio is found to be quite low,indicating deep mixing in these red giants. The mean value for theentire sample is <12C/13C>=4.3+/-0.4(σ=1.3), with nine stars equal, within the errors, to theequilibrium ratio 12C/13C=3.5 and two stars havingslightly higher values. There is no correlation between the12C/13 C and the abundance of iron. In addition,no correlation of 12C/13C with [12C/Fe]is found (all giants are deeply mixed), although the derived abundancesof [12C/Fe] show a positive correlation with [O/Fe] and ananticorrelation with [Na/Fe] (with the oxygen and sodium abundancestaken from previous studies in the literature). A comparison of theisotopic carbon ratios in ω Cen with those from other globularclusters (M4, M71, NGC 6752, and 47 Tuc) and with literature oxygenabundances, may reveal a slight trend of decreasing12C/13C ratios with decreasing [O/Fe] in theentire globular cluster sample of red giants. A comparison between12C/13C and both [Na/Fe] and [Al/Fe], however,reveals no trend.
| A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
| The Evolutionary Status of the Blue Halo Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJS...26...37N&db_key=AST
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