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SOPHIE velocimetry of Kepler transit candidates
XVI. Tomographic measurement of the low obliquity of KOI-12b, a warm Jupiter transiting a fast rotator

V. Bourrier, A. Lecavelier Des Etangs, G. Hébrard, A. Santerne, M. Deleuil, J.-M. Almenara, S. C. C. Barros, I. Boisse, A. S. Bonomo, G. Bruno, B. Courcol, R. F. Díaz, G. Montagnier, C. Moutou

Abstract
We present the detection and characterization of the transiting warm Jupiter KOI-12b, first identified with Kepler with an orbital period of 17.86 days. We combine the analysis of Kepler photometry with Doppler spectroscopy and line-profile tomography of time-series spectra obtained with the SOPHIE spectrograph to establish its planetary nature and derive its properties. To derive reliable estimates for the uncertainties on the tomographic model parameters, we devised an empirical method of calculating statistically independent error bars on the time-series spectra. KOI-12b has a radius of 1.43 ± 0.13RJup and a 3σ upper mass limit of 10 MJup. It orbits a fast-rotating star (vsini = 60.0 ± 0.9 km s-1) with mass and radius of 1.45 ± 0.09M and 1.63 ± 0.15R, located at 426 ± 40 pc from the Earth. Doppler tomography allowed higher precision on the obliquity to be reached by comparison with analysis of the Rossiter-McLaughlin radial velocity anomaly, and we find that KOI-12b lies on a prograde, slightly misaligned orbit with low sky-projected obliquity λ = 12.6. The properties of this planetary system, with a 11.4 mag host star, make of KOI-12b a precious target for future atmospheric characterization.

Keywords
planetary systems, stars: individual: KOI-12, techniques: photometric, techniques: radial velocities, techniques: spectroscopic

Astronomy and Astrophysics
Volume 579, Number of pages A55
2015 July

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia