The contact eclipsing binary system XX Leonis (p = 0.97 days, Sp A9) has been analysed using the PHOEBE programme, based on the Wilson–Devinney code. The BVRI light curves were obtained during spring 2006 using the 20-cm telescope and ST-7 CCD detector. The effective temperature of the primary component determined from the photometric analysis is T = (7342 ± 14) K, the inclination of the orbit is i = (84.83 ± 0.29)° and the photometric mass ratio q = (0.40 ± 0.01). The third-body hypothesis was also suggested; based on a period analysis using 57 minimum times this gave a period for the third body of p3 = (59.66 ± 0.05) yr, an amplitude of A = (0.036 ± 0.028) day and zero eccentricity, which yields as a minimum mass M3,min = (0.91 ± 0.01) M⊙.
