BEER analysis ofKeplerand CoRoT light curves

Abstract

Context. The BEER algorithm searches stellar light curves for the BEaming, Ellipsoidal, and Reflection photometric modulations that are caused by a short-period companion. These three effects are typically of very low amplitude and can mainly be detected in light curves from space-based photometers. Unlike eclipsing binaries, these effects are not limited to edge-on inclinations. Aims. Applying the algorithm to wide-field photometric surveys such as CoRoT and Kepler offers an opportunity to better understand the statistical properties of short-period binaries. It also widens the window for detecting intrinsically rare systems, such as shortperiod brown-dwarf and massive-planetary companions to main-sequence stars. Methods. Applying the search to the first five long-run center CoRoT fields, we identified 481 non-eclipsing candidates with periodic flux amplitudes of 0.5-87 mmag. Optimizing the Anglo-Australian-Telescope pointing coordinates and the AAOmega fiberallocations with dedicated softwares, we acquired six spectra for 231 candidates and seven spectra for another 50 candidates in a seven-night campaign. Analysis of the red-arm AAOmega spectra, which covered the range of 8342-8842 Å, yielded a radial-velocity precision of ∼1 km s −1 . Spectra containing lines of more than one star were analyzed with the two-dimensional correlation algorithm TODCOR. Results. The measured radial velocities confirmed the binarity of seventy of the BEER candidates -45 single-line binaries, 18 doubleline binaries, and 7 diluted binaries. We show that red giants introduce a major source of false candidates and demonstrate a way to improve BEER's performance in extracting higher fidelity samples from future searches of CoRoT light curves. The periods of the confirmed binaries span a range of 0.3-10 days and show a rise in the number of binaries per ΔlogP toward longer periods. The estimated mass ratios of the double-line binaries and the mass ratios assigned to the single-line binaries, assuming an isotropic inclination distribution, span a range of 0.03-1. On the low-mass end, we have detected two brown-dwarf candidates on a ∼1 day period orbit. Conclusions. This is the first time non-eclipsing beaming binaries are detected in CoRoT data, and we estimate that ∼300 such binaries can be detected in the CoRoT long-run light curves.

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