A search for starlight reflected from υ And's innermost planet




In data from three clear nights of échelle spectroscopy in 2000 October/November, and using improved Doppler tomographic signal-analysis techniques, we have carried out a deep search for starlight reflected from the innermost of υ (upsilon) And's three planets. We place upper limits on the planet's radius Rp as functions of its projected orbital velocity Kp≈139 sin i km s−1 for various assumptions about the wavelength-dependent geometric albedo spectrum p(λ) of its atmosphere. For a grey albedo p we find inline image, with 0.1 per cent false-alarm probability (4σ). For a Sudarsky, Burrows & Pinto Class V model atmosphere, the mean albedo in our 380–676 nm bandpass is 〈p〉∼0.42, requiring Rp<1.51RJ, whereas an (isolated) Class IV model with 〈p〉∼0.19 requires Rp<2.23RJ. The star's vrot sin i∼10 km s−1 and estimated rotation period Prot∼10 d suggest a high orbital inclination i∼70°–80°. We also develop methods for assessing the false-alarm probabilities of faint candidate detections, and for extracting information about the albedo spectrum and other planetary parameters from faint reflected-light signals.