Puzzling Locations of Mildly Metal-Poor Stars in the HR Diagram

Figure 1.

Location in the HR diagram of stars in the metallicity range [-2.2 < [Fe/H] < -1.8] and comparison with the [Fe/H] = -1.98 Bergbusch and Vandenberg (1992) 14 Gyrs isochrone (dotted line). The shift needed in Teff is indicated by the arrow. Dashed lines show 12 and 16 Gyrs similarly shifted isochrones.

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