Revisiting the helium abundance in globular clusters with multiple main sequences

For nearby K dwarfs, the bloadening of the observed Mam Sequence at low metallicities is much narrower than expected from isochiones with the standard helium-to-metal enrichment iatio Delta Y/Delta Z similar to 2 A much higher value, of older 10, is formally needed to reproduce the observed broadening, but it returns helium abundances in awkward contrast with Big Bang Nucleosynthesis This steep enrichment ratio resembles, on a milder scale, the very high Delta Y/Delta Z estimated from the multiple Mam Sequences observed in sonic metal-poor Globular Clusters We argue that a revision of low Main Sequence stellar models, suggested from nearby stars, conk! help to reduce the own whelmingly high Delta Y/Delta Z deduced so fat for those clusters Under the most favourable assumptions, the estimated helium content, lot the em idled populations may decrease from Y similar or equal to 0 4 to as low as Y similar or equal to 0 3, with intermediate values being plausible