S. Rappaport, K. Deck, A. Levine, T. Borkovits, J. Carter, I. El Mellah, R. Sanchis Ojeda, B. Kalomeni
We present the results of a search through the photometric database of eclipsing Kepler binaries (Prsa et al. 2011; Slawson et al. 2011) looking for evidence of hierarchical triple star systems. The presence of a third star orbiting the binary can be inferred based on binary eclipse timing variations. We apply a simple algorithm in an automated determination of the eclipse times for all 2157 binaries. The "calculated" eclipse times, based on a constant period (Keplerian, or two-body) model, are subtracted from those observed. The resulting O-C (observed minus calculated times) curves are then visually inspected for periodic residuals in order to find triple-star candidates. After eliminating false positives due to the beat frequency between the ~1/2-hour Kepler cadence and the binary period, 39 candidate triple systems were found. The periodic O-C curves for these candidates were then fit for contributions from both the classical Roemer delay and so-called "physical" delay, in an attempt to extract a number of the system parameters of the triple. We discuss the limitations of the information that can be inferred from these O-C curves without further supplemental input, e.g., ground-based spectroscopy. Based on the limited range of periods for the triples to which this search is sensitive, we can extrapolate to estimate that at least 20% of all close binaries have tertiary companions.
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http://arxiv.org/abs/1302.0563
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