On the primordial helium abundance and spectroscopic uncertainties Academic Article uri icon


  • To assess the uncertainties in primordial helium abundance determination by nebular codes, we calculate a grid of OB stellar atmospheres at low metallicities, including both non-local thermodynamic equilibrium (NLTE) and metal line blanketing effects. The more sophisticated stellar atmosphere models we use can differ from LTE models by as much as 40% in the ratio of He to H-ionizing photons.

publication date

  • January 1, 1999