Apsidal motion and light a curve solution for eighteen SMC eccentric eclipsing binaries

TL;DR

This study analyzes the apsidal motion and light curves of eighteen eccentric eclipsing binaries in the Small Magellanic Cloud, deriving new minima timings and apsidal motion parameters to improve understanding of their orbital dynamics.

Contribution

The paper provides the first detailed analysis of apsidal motion periods and light curve parameters for eighteen SMC eccentric binaries, including detection of third light in some systems.

Findings

Apsidal motion periods refined to 19-142 years.

Relativistic effects contribute up to 10% of apsidal motion.

Third light detected in several systems, indicating additional companions.

Abstract

Aims: The Danish 1.54-meter telescope at the La Silla observatory was used for photometric monitoring of selected eccentric eclipsing binaries located in the Small Magellanic Cloud. The new times of minima were derived for these systems, which are needed for accurate determination of the apsidal motion. Moreover, many new times of minima were derived from the photometric databases OGLE and MACHO. Eighteen early-type eccentric-orbit eclipsing binaries were studied. Methods: Their (O-C) diagrams of minima timings were analysed and the parameters of the apsidal motion were obtained. The light curves of these eighteen binaries were analysed using the program PHOEBE, giving the light curve parameters. For several systems the additional third light also was detected. Results: We derived for the first time and significantly improved the relatively short periods of apsidal motion from 19 to 142 years for these systems. The relativistic effects are weak, up to 10% of the total apsidal motion rate. For one system (OGLE-SMC-ECL-0888), the third-body hypothesis was also presented, which agrees with high value of the third light for this system detected during the light curve solution.