Free Access

Fig. 1


M3 HB stars compared to theoretical HB models with Z = 0.001 in the Strömgren y vs. (by) plane. The upper panel is a zoom-in around the ZAHB locus. PGPUC ZAHB loci are shown for helium abundances Y = 0.246 (red line), 0.256 (blue line, shown in the upper panel only, for clarity), and 0.266 (green line). C09 and BaSTI ZAHB loci for Y = 0.246 are also shown as magenta and black lines, respectively, with different distance moduli in order to match the PGPUC ZAHB locus with Y = 0.246. Theoretical HB evolutionary tracks for Y = 0.246 are shown as red dot-dashed lines for MHB = 0.582, 0.596, 0.609, 0.632, 0.652, 0.665, and 0.800 M, which have been marked with circles at the ZAHB, MAHB, and 90AHB (colors depend on the HB mass, for clarity). An additional HB track for Y = 0.256 and MHB = 0.582 M is also shown in the top panel (blue dot-dashed lines with pink circles). Vertical dot-dashed lines indicate some Teff values at the ZAHB locus for Y = 0.246. The distance modulus was selected as described in Sect. 3.3 and Fig. 6. The data come from C09.

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.