AAVSO: American Association of Variable Star Observers

BVRI Photometric Study of High Mass Ratio, Detached, Pre-contact W UMa Binary GQ Cancri

Volume 45 number 2 (2017)

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Ronald G. Samec
Natural Sciences Dept. Emmanuel College,181 Springs St., Franklin Springs, GA 30639
Amber Olson
Natural Sciences Dept. Emmanuel College,181 Springs St., Franklin Springs, GA 30639
Daniel Caton
Dark Sky Observatory, Department of Physics and Astronomy, Appalachian State University, 525 Rivers Street, Boone, NC 28608
Danny R. Faulkner
Johnson Observatory, 1414 Bur Oak Ct., Hebron, KY 41048


CCD BVRcIc light curves of GQ Cancri were observed in April 2013 using the SARA North 0.9-meter Telescope at Kitt Peak National Observatory in Arizona in remote mode. It is a high-amplitude (V ~ 0.9 magnitude) K0–V type eclipsing binary (T1 ~ 5250 K) with a photometrically-determined mass ratio of M2 / M1 = 0.80. Its spectral color type classifies it as a pre-contact W UMa Binary (PCWB). The Wilson-Devinney Mode 2 solutions show that the system has a detached binary configuration with fill-outs of 94% and 98% for the primary and secondary component, respectively. As expected, the light curve is asymmetric due to spot activity. Three times of minimum light were calculated, for two primary eclipses and one secondary eclipse, from our present observations. In total, some 26 times of minimum light covering nearly 20 years of observation were used to determine linear and quadratic ephemerides. It is noted that the light curve solution remained in a detached state for every iteration of the computer runs. The components are very similar with a computed temperature difference of only 4 K, and the flux of the primary component accounts for 53–55% of the system’s light in B, V, Rc, and Ic. A 12-degree radius high latitude white spot (faculae) was iterated on the primary component.