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Fig. 1


Distribution of helium abundance versus Teff for the subdwarf population from the SPY sample (Lisker et al. 2005; Stroeer et al. 2007; Hirsch 2009). The dashed lines mark the range of iHe subdwarfs. The two heavy-metal subdwarfs from SPY (Naslim et al. 2013) and the prototypical heavy-metal subdwarfs LS IV − 14°116 (Naslim et al. 2011) and [CW83] 0825+15 (Jeffery et al. 2017)are marked by blue triangles, HD 127493 and HZ 44 in red. Open symbols represent C-poor, N-rich stars, filled symbols represent C-rich stars.

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