NOAO >   Observing Info >   Approved Programs >   2010A-0392

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Proposal Information for 2010A-0392


PI: Andrea Dupree, Harvard-Smithsonian CfA, dupree@cfa.harvard.edu
Address: Solar, Stellar, Planetary Division, 60 Garden Street, MS-15, Cambridge, MA 02138, USA

CoI: Graeme H. Smith, Lick Observatory
CoI: Jay Strader, Harvard-Smithsonian CfA

Title: Sleuthing the Abundance of Helium in Omega Centauri

Abstract: The presence of a large helium abundance inhomogeneity in the globular cluster Omega Centauri, signaled by a bifurcation of colors in the middle main sequence, can be tested directly. We propose a measure of the strength of the \ionHe1 10830Aabsorption line in stars on the red giant branch of the cluster. Helium absorption occurs in metal- poor stars with T_eff > 4500K both in the field and in the clusters, M4 and M13. PHOENIX spectra of a sample of red giants in Omega Cen can reveal the presence (or not) of a bimodal distribution of helium equivalent widths in a sample of red giants not subject to diffusion or abundance stratification.


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NOAO >   Observing Info >   Approved Programs >   2010A-0392

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