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Figure 1: The effective temperatures and surface gravities derived for our hottest target stars (formal errors only). Helium-poor, solar helium, and helium-rich stars are marked by red, green, and blue squares, respectively. The solid lines mark the canonical HB locus for [M/H] = -1.5 from Moehler et al. (2003). The tracks for an early hot flasher (long-dashed line) and a late hot flasher (short-dashed line) show the evolution of such stars from the zero-age HB (ZAHB) towards helium exhaustion in the core (terminal-age HB = TAHB). The dotted line connects the series of ZAHB models computed by adding a hydrogen-rich layer to the surface of the ZAHB model of the late hot flasher. The small dots mark - with decreasing temperature - hydrogen layer masses of 0, 10-7, 10-6, 10-5, 10-4  (for details see Moehler et al. 2002).

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In the text

	Figure 2: The effective temperatures and helium abundances for our hottest target stars (formal errors only). The dashed line marks solar helium abundance, the hashed area marks the range for the helium-enrichment scenario. The symbols have the same meaning as in Fig. 1.
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In the text

	Figure 3: Sample spectra of stars with super-solar helium abundance, compared to model spectra with the cluster carbon abundance for metal-poor stars (red) and a carbon abundance of 3% by mass (blue). The labels give the number of the star, its effective temperature, and its helium abundance .
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In the text