First Light Curve Analysis of EL Tuc Reveals Key Characteristics of Binary Star System

A recent analysis has been conducted on the binary star system EL Tuc, marking the first light curve study within the framework of the Binary Systems of South and North (BSN) Project. The research was carried out by Elham Sarvari, Eduardo Fernández Lajús, and Atila Poro, and the findings were submitted on August 30, 2024, to the arXiv repository under the identifier arXiv:2408.17077.

Photometric observations were performed using standard multiband BVRI filters at an observatory in Argentina. The study presents a new ephemeris for EL Tuc and includes a linear fit to the O-C diagram, utilizing extracted times of minima along with additional literature data. The analysis employed the PHysics Of Eclipsing BinariEs (PHOEBE) Python code and the Markov chain Monte Carlo (MCMC) approach for the light curve analysis.

The results indicate that EL Tuc is classified as a total contact binary system with a low mass ratio of q=0.172±0.002, an orbital inclination of i=83.74±0.40 degrees, and a fillout factor of f=53.7±1.6%. Notably, the light curve solution required the presence of a cold starspot on the hotter component of the system.

Furthermore, the researchers utilized the P-a relationship and the Gaia Data Release 3 (DR3) parallax method to determine the absolute parameters of EL Tuc, allowing for a comparison of the precision of their results. The system was classified as W-type based on the mass and effective temperature of the companion stars. The positions of the systems were depicted on various diagrams, including mass-luminosity and mass-radius diagrams, and the relationship between spectroscopic and photometric mass ratios of binaries was discussed.

This research contributes to the understanding of binary star systems and their characteristics, providing valuable data for future studies in stellar astrophysics.