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Stellar models generally use simple parametrizations to treat convection. Themost widely used parametrization is the so-called "Mixing Length Theory" wherethe convective eddy sizes are described using a single number, \alpha, themixing-length parameter. This is a free parameter, and the general practice isto calibrate \alpha using the known properties of the Sun and apply that to allstars. Using data from NASA's Kepler mission we show that using thesolar-calibrated \alpha is not always appropriate, and that in many cases itwould lead to estimates of initial helium abundances that are lower than theprimordial helium abundance. Kepler data allow us to calibrate \alpha for manyother stars and we show that for the sample of stars we have studied, themixing-length parameter is generally lower than the solar value. We studied thecorrelation between \alpha and stellar properties, and we find that \alphaincreases with metallicity. We therefore conclude that results obtained byfitting stellar models or by using population-synthesis models constructed withsolar values of \alpha are likely to have large systematic errors. Our resultsalso confirm theoretical expectations that the mixing-length parameter shouldvary with stellar properties.

Calibrating Convective properties of Solar-like Stars in the Kepler Field of View