The Photometric Study of Six W UMa Systems and Investigation of the Mass-Radius Relations for Contact Binary Stars

TL;DR

This study analyzes six W UMa contact binary systems through photometry, investigates their orbital period changes, and refines mass-radius relations, providing new insights into contact binary star properties and their evolutionary trends.

Contribution

It presents the first detailed photometric analysis of five systems, uses MCMC for orbital variation trends, and updates mass-radius relations for contact binaries with comparisons to spectroscopic data.

Findings

V336 TrA and PS Boo show likely orbital growth.

Four systems exhibit linear orbital period trends, possibly due to measurement errors.

New mass-radius and mass ratio-radius ratio relations for W UMa systems are established.

Abstract

We present the photometric analysis of six short-period systems (EI Oct, V336 TrA, NX Boo, V356 Boo, PS Boo, and V2282 Cyg). This is the first photometric analysis of these systems except for V336 TrA. Observations were conducted for 27 nights at three observatories in the northern and southern hemispheres. We calculated a new ephemeris for each of the systems using our minimum times and additional literature. The Markov Chain Monte Carlo (MCMC) approach was used to determine the eclipse timing variation trends of the systems. We found a likely orbital growth for V336 TrA and PS Boo; four other systems show a linear trend in orbital period changes, which is most likely due to the accumulation of measurement errors in their linear ephemeris parameters. The light curve analysis was performed using the Physics of Eclipsing Binaries (PHOEBE) 2.3.59 version code with the MCMC approach. The absolute parameters of the systems were calculated by using the Gaia Early Data Release 3 (EDR3) parallax. The positions of the systems were also depicted on the Hertzsprung-Russell (H-R) and $logJ_0-logM$ diagrams. According to a sample, we were able to present relations for the mass-radius (M-R) relationships of contact binary systems. There is also a strong relationship between the mass ratio and the radius ratio in the W UMa systems for which we also provided a new relation. We compared the M-R updated relationships in this study with seven systems in other studies obtained using the spectroscopic method. In addition, we estimated some of the absolute parameters for 1734 EW systems, based on the new relationships.