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Fig. 4

image

Location of the GB sample stars in the Hertzsprung-Russell diagram overlayed on evolutionary tracks on the AGB from Bertelli et al. (2008, 2009) for solar composition. Tracks are for main-sequence masses 0.7 MMS 6.0 M. Segments of the tracks, where the photospheric chemical composition is C-rich, are shown in red (dotted). Stars with envelopes of unknown chemistry are plotted with asterisks. Average luminosities of the GB sample stars are taken from Table 3. For the unknown effective temperatures random values between 2500 and 2800 K were adopted.

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