KEPLERECLIPSING BINARIES WITH STELLAR COMPANIONS

Abstract

Many short-period binary stars have distant orbiting companions that have played a role in driving the binary components into close separation. Indirect detection of a tertiary star is possible by measuring apparent changes in eclipse times of eclipsing binaries as the binary orbits the common center of mass. Here we present an analysis of the eclipse timings of 41 eclipsing binaries observed throughout the NASA Kepler mission of long duration and precise photometry. This subset of binaries is characterized by relatively deep and frequent eclipses of both stellar components. We present preliminary orbital elements for seven probable triple stars among this sample, and we discuss apparent period changes in seven additional eclipsing binaries that may be related to motion about a tertiary in a long period orbit. The results will be used in ongoing investigations of the spectra and light curves of these binaries for further evidence of the presence of third stars.

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

“…There is a small displacement of the secondary eclipse from the exact phase 0.5, by ∼18.7 min, or 0.00053 P. The measurements of eclipse times, given separately for the primary and secondary by Gies et al (2015), seem to confirm that by showing a gradual diverging, which suggests apsidal motion. The RV fit was therefore done with values of e and ω fixed to those found in the LC fit.…”

“…Having v γ, A = 0 means that the tertiary is in fact not gravitationally bound (a blend), or the period of the AB orbit is too long to see the motion in the RVs. We mentioned before that the ETVs reported by Gies et al (2015) show a small curvature, as well as a gradual diverging. We have calculated our own ETVs, which we present in Figure 16.…”

“…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.…”

“…The RV fit was therefore done with values of e and ω fixed to those found in the LC fit. The ETVs of Gies et al (2015) also show a small curvature (nonzero time derivative of the orbital period, P), which can be explained either by a presence of a third body, or a mass transfer. The latter seems unlikely, as the stars are far from filling their Roche lobes, and a clear detection of a third set of lines in the spectra supports the former scenario.…”

“…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.…”