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

TL;DR

This paper clarifies the proper use of gravity darkening coefficients in the JKTEBOP eclipsing binary code, emphasizing the distinction between wavelength-dependent coefficients and bolometric exponents to avoid biases.

Contribution

It highlights the common confusion between gravity darkening coefficients and exponents, providing guidance on correct application in light curve analysis.

Findings

Incorrect use of coefficients can bias results

Wavelength-dependent coefficients differ significantly from bolometric exponents

Proper application improves accuracy of eclipsing binary models

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.