2007A&A...468..657G

We evaluate the effects that variations in He content have on bolometric corrections and T_eff-colour relations. To do this, we computed ATLAS9 model atmospheres and spectral energy distributions for effective temperatures ranging from 3500K to 40000K for dwarfs and from 3500K to 8000K for giants, considering both ``He-non-enhanced'' and ``He-enhanced'' compositions. The variations in He content that were considered are of ΔY=+0.1 and +0.2 for the metallicity [M/H]=+0.5 and ΔY = +0.1 for [M/H]=-0.5 and -1.5. Synthetic photometry was then carried out for the UBVRIJHK system. We conclude that the changes in bolometric corrections, caused by the adopted He-enhancements are in general too small (less than 0.01mag), for both dwarfs and giants, to be affecting present-day tables of bolometric corrections at a significant level. The only possible exceptions are found for the U-band at T_eff between 4000K and 8000K, where |ΔBC_U| amounts to ∼0.02mag, and for T_eff equal to 3500K, where |ΔBC_Sλ| values clearly become much higher (up to 0.06mag for passbands from U to V). However, even in the latter case the overall uncertainty caused by variations in the He content may be not so significant, because the ATLAS9 results are still approximative at their lowest temperature limit.