# The first study of the light-travel time effect in bright eclipsing binaries in the Small Magellanic Cloud

## TL;DR

This study investigates period variations and third-body effects in the brightest eclipsing binaries of the Small Magellanic Cloud using extensive photometric data and light curve analysis, revealing new insights into their orbital dynamics.

## Contribution

First comprehensive analysis of period changes and third bodies in SMC eclipsing binaries using combined survey and CCD data.

## Key findings

- 14 systems have additional bodies with orbital periods from 2 to 20 years.
- Approximately 10% of systems show eccentric orbits.
- Similar proportions exhibit third bodies and asymmetric light curves.

## Abstract

The first 100 brightest eclipsing systems from the Small Magellanic Cloud were studied for their period changes. The photometric data from the surveys OGLE-II, OGLE-III, OGLE-IV and MACHO were combined with our new CCD observations obtained using the Danish 1.54-m telescope (La Silla, Chile). Besides the period changes the light curves were also analysed using the program PHOEBE, which provided the physical parameters of both eclipsing components. For 14 of these systems the additional bodies were found, having the orbital periods from 2 to 20 yr and the eccentricities were found to be up to 0.9. Amongst the sample of studied 100 brightest systems, we discussed the number of systems with particular period changes. About 10 per cent of these stars show eccentric orbit, about the same numbers have third bodies and about the same show the asymmetric light curves.