On the correct use of gravity darkening coefficients in the JKTEBOP eclipsing binary code

Abstract

Users of the JKTEBOP code to solve the light curves of eclipsing binaries often confuse the gravity darkening coefficients, $y(\lambda)$, with the bolometric gravity darkening exponents, $\beta$. JKTEBOP requires the wavelength-dependent coefficients. I show that the numerical values of $y(\lambda)$ and $\beta$ can be rather different, leading to potential biases in the solution if the wrong quantities are used.