Effective temperatures of cool metal-poor stars derived from the analysis of 3D Balmer lines

Balmer lines are recognized as accurate indicators of the effective temperature of late‐type stars. The influence of convection on the shape of Balmer line profiles has been investigated using LTE 3D hydrodynamical model atmospheres and ‘classical’ LTE 1D stellar atmospheres, where convection is modeled within the simplistic picture of mixing‐length theory. Models and line profiles computed with the CO5BOLD and Linfor3D codes have been used to determine the effective temperatures of the Sun and three well known metal‐poor stars HD84937, HD74000, and HD140283. Our 3D fit provides the best fit thus far for the solar Hα temperature using the Barklem theory. The resulting (3D‐1D) Teff biases related to the different treatment of convection in the 1D and 3D models are presented.