Apsidal motions of 90 eccentric binary systems in the Small Magellanic Cloud

TL;DR

This study identified 90 new eccentric binary systems in the Small Magellanic Cloud exhibiting apsidal motion, significantly expanding the known sample and providing detailed analysis of their orbital characteristics.

Contribution

The paper reports the discovery of 90 new apsidal motion binaries in the SMC, tripling the previously known sample and analyzing their orbital periods and potential third-body effects.

Findings

Apsidal motion periods range from 12 to 897 years.

Detected short-term oscillations in four systems suggest third bodies.

Sample size increased by a factor of about 3.

Abstract

We examined light curves of 1138 stars brighter than 18.0 mag in the $I$ band and less than a mean magnitude error of 0.1 mag in the $V$ band from the OGLE-III eclipsing binary catalogue, and found 90 new binary systems exhibiting apsidal motion. In this study, the samples of apsidal motion stars in the SMC were increased by a factor of about 3 than previously known. In order to determine the period of the apsidal motion for the binaries, we analysed in detail both the light curves and eclipse timings using the MACHO and OGLE photometric database. For the eclipse timing diagrams of the systems, new times of minimum light were derived from the full light curve combined at intervals of one year from the survey data. The new 90 binaries have apsidal motion periods in the range of 12$-$897 years. An additional short-term oscillation was detected in four systems (OGLE-SMC-ECL-1634, 1947, 3035, and 4946), which most likely arises from the existence of a third body orbiting each eclipsing binary. Since the systems presented here are based on homogeneous data and have been analysed in the same way, they are suitable for further statistical analysis.