A CCD photometric study of the late type contact binary EK Comae Berenices

TL;DR

This study provides new CCD photometric observations of the contact binary EK Comae Berenices, revealing a change in light curve shape and reclassifying it from W-type to A-type, with detailed system parameters derived.

Contribution

It offers the first detailed CCD-based analysis showing EK Comae Berenices is an A-type W UMa binary, correcting previous classifications and providing precise system parameters.

Findings

Light curve shape has changed significantly since previous observations.

EK Comae Berenices is an A-type, totally eclipsing W UMa binary.

The system exhibits the O'Connell effect explained by a hot spot.

Abstract

We present CCD photometric observations of the W UMa type contact binary EK Comae Berenices using the 2 metre telescope of $IUCAA$ Girawali Observatory, India. The star was classified as a W UMa type binary of subtype-W by \citet{sam1996}. The new V band photometric observations of the star reveal that shape of the light curve has changed significantly from the one observed by \citet{sam1996}. A detailed analysis of the light curve obtained from the high-precision CCD photometric observations of the star indicates that EK Comae Berenices is not a W-type but an A-type totally eclipsing W UMa contact binary. The photometric mass ratio is determined to be 0.349 $\pm$ 0.005. A temperature difference of $\Delta T = 141 \pm 10 $ K between the components and an orbital inclination of $i [^{o}] = 89.800 \pm 0.075$ were obtained for the binary system. Absolute values of masses, radii and luminosities are estimated by means of the standard mass-luminosity relation for zero age main-sequence stars. The star shows O'Connell effect, asymmetries in the light curve shape around the primary and secondary maximum. The observed O'Connell effect is explained by the presence of a hot spot on the primary component.