Close Binary System GO Cyg

TL;DR

This study analyzes long-term photometric variations of the close binary system GO Cyg, revealing its physical parameters, near-contact status, and evidence of a third body affecting its orbital period.

Contribution

It provides detailed physical parameters of GO Cyg and identifies a third body causing sinusoidal period variations, which is a novel insight into this system.

Findings

GO Cyg is a near-contact binary with a primary filling its Roche lobe.

A third body with less than 2.3 solar masses influences the system's period.

The period variation rate is measured at -1.4×10^{-9} days per year.

Abstract

In this study, we present long term photometric variations of the close binary system \astrobj{GO Cyg}. Modelling of the system shows that the primary is filling Roche lobe and the secondary of the system is almost filling its Roche lobe. The physical parameters of the system are $M_1 = 3.0\pm0.2 M_{\odot}$, $M_2 = 1.3 \pm 0.1 M_{\odot}$, $R_1 = 2.50\pm 0.12 R_{\odot}$, $R_2 = 1.75 \pm 0.09 R_{\odot}$, $L_1 = 64\pm 9 L_{\odot}$, $L_2 = 4.9 \pm 0.7 L_{\odot}$, and $a = 5.5 \pm 0.3 R_{\odot}$. Our results show that \astrobj{GO Cyg} is the most massive system near contact binary (NCB). Analysis of times of the minima shows a sinusoidal variation with a period of $92.3\pm0.5$ years due to a third body whose mass is less than 2.3$M_{\odot}$. Finally a period variation rate of $-1.4\times10^{-9}$ d/yr has been determined using all available light curves.