Short-Period Light Variation of an Eclipsing Binary System: RZ Cassiopeiae

Abstract

The eclipsing binary system RZ Cas is known to exhibit variation in its light curves at the primary minimum, usually showing a partial-eclipse–type curve but sometimes indicating a flat minimum, which is evidence for a total eclipse. We observed RZ Cas not only during the primary eclipse, but also during the out-of-eclipse phase, and we have found a short-period light variation with a frequency of 62.20 cycles day-1 (period of 23.15 minutes), whose maximum amplitude is 0.02 mag. This short-period variation can modulate the shape of the light curve at the primary minimum effectively. The brightness-color relationship of the short-period variation suggests a δ Scuti type oscillation.