A study of the light travel time effect in short-period MOA eclipsing binaries via eclipse timing

A sample of 542 eclipsingbinaries (EBs) with periods shorter than 2 days were selected from the MOA EB catalogue for eclipsetime variation analysis. For this sample we were able to obtain the time series from MOA-II that span 9.5 years. We discovered 91 EBs, among these 542 EBs, with detected light-travel-time effect signals suggesting the presence of tertiarycompanions of orbiting periodsfrom 250 days to 28 years. The frequency of EBs with tertiarycompanions in our sample increases as the period decreases and reaches a value of 0.65 for contact binariesof periods shorter than 0.3 days. If only the contact binariesof periods < 0.26 days are considered, the frequency even goes to the unit. Our results suggest that contact binarieswith periods close to the 0.22-day contact binarylimit are commonly accompanied by relatively close tertiarycompanions. Furthermore, excess at extremely high eccentricity was noticed for our 91 triple candidates.