A study of the light travel time effect in short-period MOA eclipsing binaries via eclipse timing
journal contributionposted on 10.04.2019, 09:21 by MCA Li, NJ Rattenbury, IA Bond, T Sumi, DP Bennett, N Koshimoto, F Abe, Y Asakura, R Barry, A Bhattacharya, M Donachie, P Evans, A Fukui, Y Hirao, Y Itow, K Masuda, Y Matsubara, Y Muraki, M Nagakane, K Ohnishi, T Saito, A Sharan, DJ Sullivan, D Suzuki, PJ Tristram, A Yonehara
A sample of 542 eclipsing binaries (EBs)with periods shorter than 2 days was selected from the Microlensing Observations in Astrophysics (MOA) EB catalogue (Li et al.) for eclipse-time variation analysis. For this sample, we were able to obtain a time series from MOA-II spanning 9.5 yr. We discovered 91 EBs, out of the 542 EBs, with detected light-travel-time effect signals suggesting the presence of tertiary companions with orbiting periods from 250 d-28 yr. The frequency of EBs with tertiary companions in our sample increases as the period decreases and reaches a value of 0.65 for contact binaries with periods shorter than 0.3 d. If only those contact binaries with periods < 0.26 d are considered, the frequency even goes to unity. Our results suggest that contact binaries with periods close to the 0.22-d contact binary limit are commonly accompanied by relatively close tertiary companions.