TRIPLE-STAR CANDIDATES AMONG THEKEPLERBINARIES

Abstract

We present the results of a search through the photometric database of Kepler eclipsing binaries (Prša 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 from 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 model, are subtracted from those observed. The resulting O − C (observed minus calculated times) curves are then visually inspected for periodicities 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 identified. 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 orbital periods for the triple star systems to which this search is sensitive, we can extrapolate to estimate that at least 20% of all close binaries have tertiary companions.

ξTauri: a unique laboratory to study the dynamic interaction in a compact hierarchical quadruple system

“…The first-order model of the physical delay (Eq. (8) from Rappaport et al 2013), which is only a part of the total ETV, arising from dynamical interaction of two orbits in hierarchical triple systems, gives an estimate of the amplitude of the effect ∆t MODEL ≈ 0.02 d, (i.e. in rough agreement with the detected value).…”

“…Assuming for simplicity coplanar orbitsJ = 0 deg, we obtain (e.g. Soderhjelm 1975;Borkovits et al 2011Borkovits et al , 2015Rappaport et al 2013, which also contain terms proportional to ∝J 2 )…”

KEPLERECLIPSING BINARIES WITH STELLAR COMPANIONS

“…These surveys indicate that 18% » of the observed systems display variations consistent with orbital motion about a third star. Detailed case studies of specific triples have been presented by Rappaport et al (2013), Borkovits et al (2015), and Zasche et al (2015), among others. Furthermore, Kepler light curves have uncovered a number of remarkable cases in which the orientation of the outer system is such that eclipses by the tertiary are also observed (Carter et al 2011;Derekas et al 2011;Armstrong et al 2012;Borkovits et al 2013).…”

Orbital period changes and the higher-order multiplicity fraction amongst SuperWASP eclipsing binaries

“…However, a more widely-applicable technique will be the detection of eclipse timing variations producing an approximately sinusoidal curve in an O−C (observed minus calculated) diagram, as in Lohr et al (2013a), where a triple system containing an M+M contact binary was proposed on such evidence, and later confirmed by Tables A.1 to A.6 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A136 Koen (2014), in Lohr et al (2014) also, period variations arguably produced by circumbinary planets were detected in several post-common-envelope binaries. This approach was used by Rappaport et al (2013) to search for candidate triples in the Kepler eclipsing binary catalogue. Here, we use a preliminary catalogue of candidate SuperWASP eclipsing binaries to search for orbital period changes potentially indicative of third bodies.…”