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CCD photometric study of the short period contact binary CE Leonis
Light curves and photometric solutions of the contact binary CE Leo arepresented in this paper. The light curves appear to exhibit a typicalO'Connell effect, with Maximum I being 0.045 mag (V) and 0.048 mag (B)brighter than Maximum II, respectively, and Maximum I shifting to phase0.26. The new light curve and those published by Samec et al. (1993)show the change in shape of the light curves of the system. From 1989 to2001, the difference in the depths between the primary and secondaryeclipses increased by 0.100 mag (V) and 0.113 mag (B). The orbitalperiod of the system oscillates with a cycle of about 14 years and asemi-amplitude of 0.004 days. The light curves are analyzed by means ofthe latest version of the Wilson-Devinney code. The results show that CELeo is a W-subtype contact binary with a ratio q=0.501. The asymmetry ofthe light curves is explained by star spot models. Variations intemperature of the spot on the primary component may be responsible forthe light curve variation of the system. The cyclical period change canmost probably be attributed to a magnetic activity cycle in the primarycomponent.
| V432 Persei: A Contact Binary with Components in Poor Thermal Contact
CCD photometric observation of the short-period eclipsing binary V432Persei was carried out in the B and V bands at the Yunnan Observatory ofChina. The light curves of the system are obviously asymmetrical, withthe primary maximum brighter than the secondary maximum, which is knownas the O'Connell effect. The presented light curves are analyzed bymeans of the latest version of the Wilson-Devinney program. A grid ofsolutions for several fixed values of the mass ratio was calculated. Thebest fitting possible is for a mass ratio of 0.269 and a low degree ofcontact. The results show that V432 Per is seen to be a W-subtype WUrsae Majoris contact binary in poor thermal contact. The differencebetween the mean temperatures of the components is about 850 K. Theasymmetry of the light curves is explained by a cool spot on thesecondary component. The nature of the overluminosity of the secondaryof the system suggests that there should be very great energy transferfrom the primary to the secondary.
| A CCD Photometric Study of the Contact Binary V396 Monocerotis
Complete BV light curves of the W Ursae Majoris binary V396 Mon arepresented. The present CCD photometric observations reveal that thelight curves of the system are obviously asymmetric, with the primarymaximum brighter than the secondary maximum (the ``O'Connell effect'').The light curves are analyzed by means of the latest version of theWilson-Devinney code. The results show that V396 Mon is a W-subtype WUMa contact binary with a mass ratio of 0.402. The asymmetry of thelight curves is explained by a cool spot on the secondary component. Thenature of the overluminosity of the secondary of a W UMa-type system isanalyzed. It is shown that the overluminosity of the secondary isclearly related to the mass of the primary and that, for a W UMa system,the higher the mass of the primary, the greater the overluminosity ofthe secondary. In addition, the overluminosity of the secondary is alsorelated to its own density: the lower the density of the secondary, thegreater its overluminosity.
| UY Ursae Majoris: A W-subtype W UMa system with a small mass ratio
We present light curves and photometric solutions of the contact binaryUY UMa in this paper. The light curves appear to exhibit a typicalO'Connell effect, with Maximum I being 0.034 mag(V) and 0.030 mag(B)brighter than Maximum II, respectively, and Maximum I shifting to phase0.26. The light curves are analyzed by means of the latest version ofthe WD program. The results show that UY UMa is a W-subtype contactbinary with a small mass ratio q=0.134. The asymmetry of the lightcurves is explained by star spot models. From the collected data of 9UMa contact systems with a smaller mass ratio than 0.20, the nature ofthe secondaries is analyzed. The results show that the luminosities anddensities of the secondaries could be controlled by the primaries andthat the smaller the mass ratio, the stronger the control.
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