Period determination using phase dispersion minimization.

We derive a period determination technique that is well suited to the case of nonsinusoidal time variation covered by only a few irregularly spaced observations. A detailed statistical analysis allows comparison with other techniques and indicates the optimum choice of parameters for a given problem. Application to the double-mode Cepheid BK Cen demonstrates the applicability of these methods to difficult cases. Using 49 photoelectric points, we obtain the two primary oscillatory components as well as the principal mode-interaction term; the derived periods are in agreement with previous estimates.