A SEARCH FOR HIERARCHICAL TRIPLES USINGKEPLERECLIPSE TIMING

Abstract

We produce and analyze eclipse time variation (ETV) curves for some 2600 targeted main-field Kepler binaries. We find good to excellent evidence for a third body in 222 systems via either the light-travel-time (LTTE) or dynamical effect delays. Approximately half of these systems have been discussed in previous work, while the rest are newly reported here. Via detailed analysis of the ETV curves using high-level analytic approximations, we are able to extract system masses and information about the three-dimensional characteristics of the triple for 62 systems which exhibit both LTTE and dynamical delays. For the remaining 160 systems whose ETV curves are dominated by LTTE delays we are able to extract the outer orbital period, eccentricity , and longitude of periastron as well as the mass function of the triple. In general, our solutions improve upon those published earlier. New techniques of preprocessing the flux time series are applied to eliminate false positive triples and to enhance the ETV curves. The set of triples with outer orbital periods shorter than ∼2000 days is now sufficiently numerous for meaningful statistical analysis. We find that (i) as predicted, there is a peak near i m 40 • in the distribution of the triple vs. inner binary mutual inclination angles that provides strong confirmation of the operation of Kozai-Lidov cycles with tidal friction; (ii) the median eccentricity of the third-body orbits is e 2 = 0.35; (iii) there is a deficit of triple systems with binary periods 1 day and outer periods between ∼50 and 200 days which might help guide the refinement of theories of the formation and evolution of close binaries; and (iv) the substantial fraction of Kepler binaries which have third-body companions is consistent with a very large fraction of all binaries being part of triples.

KEPLERECLIPSING BINARIES WITH STELLAR COMPANIONS

“…This will cause the overall flux to drop around the time of eclipse, and the eclipse minimum will occur slightly later as the transiting star passes over the center of light on the receding (brighter) portion of the visible hemisphere. Orosz et al (2012) and Holczer et al (2015) have documented how the starspot illumination changes lead to a general anticorrelation between the local flux derivative and eclipse time deviation, and this trend is found for example in the eclipse light curve of KIC10581918 (see Figure 1.35 of Gies et al 2012). We suspect that most of the cases that show "random-walk" kinds of variations on relatively short time scales are due to starspot activity on one or both components.…”

“…These are long cadence measurements that are obtained in net exposure times of 29.4244 minutes. The associated times given in our first paper (Gies et al 2012) were based upon UTC (Coordinated Universal Time) while the current set uses TDB (Barycentric Dynamical Time 5 ), and here we report the times in reduced Barycentric Julian Date (BJD-2,400,000 days). We used the Simple Aperture Photometry (SAP) flux except in the case of KIC04678873.…”

“…We embarked on a search for eclipse timing variations among a subset of 41 eclipsing binaries that were identified prior to the start of Kepler observations (Gies et al 2012). We subsequently completed a large set of spectroscopic observations of this sample in order to derive spectroscopic orbital elements, estimate the stellar properties, compare with evolutionary codes, and explore the pulsational properties of the component stars.…”

HIDES spectroscopy of bright detached eclipsing binaries from the Kepler field – II. Double- and triple-lined objects

“…In our spectra we see two sets of wider lines, belonging to the components of the eclipsing pair, and another, narrow set coming from a third star. This system also has ETVs reported by several authors (Gies et al 2012(Gies et al , 2015Conroy et al 2014), but no secure conclusions were drawn. KIC 10987439 = KOI 7396, TYC 3561-922-1: This system has the second longest period in our sample, and the narrowest spectral lines.…”

“…Our spectroscopy allows us to revise these values. Several authors report ETVs (Gies et al 2012(Gies et al , 2015Conroy et al 2014), but attribute them to the evolution of spots on the surface of both components.…”