Limb-darkening coefficient
= Limb-darkening coefficient
{title2=$u$}
The parameter $u$ in the <linear limb-darkening law> specifies its contrast between disk centre and the limiting edge. Its interpretation requires the chosen law and interval of <frequency> or <wavelength>. A <limb-darkening coefficient> fitted to an <exoplanet transit> may trade off against the <transit impact parameter> and <planet> <radius>; it is not a direct measurement of one layer's <temperature>.