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Description
The BEER algorithm, introduced by Faigler & Mazeh (2011MNRAS.415.3921F), searches stellar lightcurves for the BEaming, Ellipsoidal, and Reflection (BEER) 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 lightcurves from space-based photometers. Unlike eclipsing binaries, these effects are not limited to edge-on inclinations. 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, like short-period brown-dwarf and massive- planetary companions to main-sequence stars. Applying the search to the first five long-run center CoRoT fields, we identified 481 non-eclipsing candidates with periodic flux amplitudes of 0.5-87mmag. Optimizing the Anglo-Australian-Telescope pointing coordinates and the AAOmega fiber-allocations with dedicated softwares, we acquired 6-7 medium-resolution spectra of 281 candidates in a seven-night campaign. Analysis of the red-arm AAOmega spectra, which covered the range of 8342-8842{AA}, yielded a radial-velocity precision of ~1 km/s. Spectra containing lines of more than one star were analyzed with the two- dimensional correlation algorithm TODCOR. The measured radial velocities confirmed the binarity of seventy of the BEER candidates, 45 single-line binaries, 18 double-line 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 lightcurves. The periods of the confirmed binaries span a range of 0.3-10days and show a rise in the number of binaries per logP bin 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 ~1day period orbit. 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 lightcurves.
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