BVRI Photometric Analysis and 73 year Period Study of the Totally Eclipsing Binary, DK Andromedae

DK And is a Sonneberg variable, first classified as an RR Lyrae type-C. It was reclassified in 2006 as a totally eclipsing W Ursae Majoris variable with a period of 0.49 d. We present complete BVRI are light curves, a period study, and a simultaneous BVRI light-curve solution. The period study, covering some 73 years, reveals a 4-sigma-level quadratic ephemeris. Our light curves shows a time of constant light in the secondary eclipse of 28 minutes making this a totally eclipsing, A-type W UMa system. The depths of eclipses are only about 0.5 mag in V due to the fairly extreme fill-out. The light curve solution reveals a component temperature difference of ∼300 K, fairly high for such variables, and an inclination of 82.5°. Although the variable is near F2V type, it shows definite dark spot activity (31° radius spot). High fill-out binarity evidently induces the convective envelopes responsible for this activity.