  Inaccurate limb-darkening models can be a significant source of error in the
analysis of the light curves for transiting exoplanet and eclipsing binary star
systems, particularly for high-precision light curves at optical wavelengths.
The power-2 limb-darkening law, $I_\lambda(\mu) = 1 -
c\left(1-\mu^{\alpha}\right)$, has recently been proposed as a good compromise
between complexity and precision in the treatment of limb-darkening. I have
used synthetic spectra based on the 3D stellar atmosphere models from the
Stagger-grid to compute the limb-darkening for several passbands (UBVRI,
CHEOPS, TESS, Kepler, etc.). The parameters of the power-2 limb-darkening laws
are optimized using a least-squares fit to a simulated light curve computed
directly from the tabulated $I_\lambda(\mu)$ values. I use the transformed
parameters $h_1 = 1-c\left(1-2^{-\alpha}\right)$ and $h_2 = c2^{-\alpha}$ to
directly compare these optimized limb-darkening parameters to the limb
darkening measured from Kepler light curves of 16 transiting exoplanet systems.
The posterior probability distributions (PPDs) of the transformed parameters
$h_1$ and $h_2$ resulting from the light curve analysis are found to be much
less strongly correlated than the PPDs for $c$ and $\alpha$. The agreement
between the computed and observed values of ($h_1$, $h_2$) is generally very
good but there are significant differences between the observed and computed
values for Kepler-17, the only star in the sample that shows significant
variability between the eclipses due to magnetic activity (star spots). The
tabulation of $h_1$ and $h_2$ provided here can be used to accurately model the
light curves of transiting exoplanets. I also provide estimates of the priors
that should be applied to transformed parameters $h_1$ and $h_2$ based on my
analysis of the Kepler light curves of 16 stars with transiting exoplanets.
