  Multiband photometric investigations for eight binary systems of the W Ursae
Majoris (W UMa)-type are presented. Six systems are presented for the first
time to analyze their light curves. All the analyzed systems have a temperature
below 5000 K and an orbital period of less than 0.28 days. We extracted primary
and secondary minima from the ground-based observations of these systems.
According to a few observations reported in the literature, linear fits were
considered in the O-C diagrams, and new ephemerides were presented. Light curve
solutions were performed using the PHysics Of Eclipsing BinariEs (PHOEBE) code.
The results of the mass ratio and fillout factor indicate that the systems are
contact binary stars. Six of them showed the O'Connell effect, and a cold
starspot on each companion was required for light curve solutions. Their
absolute parameters were estimated and evaluated by two other methods. In this
study, the empirical relationship between the orbital period and semi-major
axis was updated using a sample consisting of 414 contact binary systems and
the Monte Carlo Markov Chain (MCMC) approach. Also, using Machine Learning (ML)
and the Artificial Neural Network (ANN) model, the relationship between
$P-T_1-M_1$ was updated for a better estimation of the mass of the primary
star.
