A Possible Connection Between the Variation of Light Curve and theChange of the Orbital Period in the Contact Binary CK Bootis

The O–C curve of the contact binary CK Boo have been analyzed with Kalimeris et al. (1994) method. It is shown that the orbital period is changing in a quasi-sinusoidal form with a period of about ∼ 14 yr superposed on a secular period increase. The correlation of the variations of the light level at MinI, MaxI and II in the light curve implies that the luminosity of secondary component is variable. Comparing the change of the quasi-periodic component in the orbital period with that of the secondary's luminosity, we find that the luminosity of the secondary component and the orbital period may vary with the same cycle length ∼14 yr; the variation of the secondary's luminosity is in the same phase with that of the orbital period. This connection is different from those of the RS CVn-type close binaries (e.g. CG Cyg, V471 Tau, RT Lac). The mechanisms that may have produced this relation of the variations of the orbital period and the luminosity of the secondary are also discussed. This revised version was published online in July 2006 with corrections to the Cover Date.