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The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet

X. Dumusque, A. S. Bonomo, R. D. Haywood, L. Malavolta, D. SÚgransan, L. A. Buchhave, A. Collier Cameron, D. W. Latham, E. Molinari, F. Pepe, S. Udry, D. Charbonneau, R. Cosentino, C. D. Dressing, P. Figueira, A. F. Martinez Fiorenziano, S. Gettel, A. Harutyunyan, K. Horne, M. Lˇpez-Morales, C. Lovis, M. Mayor, G. Micela, F. Motalebi, V. Nascimbeni, D. F. Phillips, G. Piotto, D. Pollacco, D. Queloz, K. Rice, D. Sasselov, A. Sozzetti, A. Szentgyorgyi, C. A. Watson

Abstract
Kepler-10b was the first rocky planet detected by the Kepler satellite and con- firmed with radial velocity follow-up observations from Keck-HIRES. The mass of the planet was measured with a precision of around 30%, which was insufficient to constrain models of its internal structure and composition in detail. In addition to Kepler-10b, a second planet transiting the same star with a period of 45 days was statistically validated, but the radial velocities were only good enough to set an upper limit of 20 Mearth for the mass of Kepler-10c. To improve the precision on the mass for planet b, the HARPS-N Collaboration decided to observe Kepler-10 intensively with the HARPS-N spectrograph on the Telescopio Nazionale Galileo on La Palma. In to- tal, 148 high-quality radial-velocity measurements were obtained over two observing seasons. These new data allow us to improve the precision of the mass determina- tion for Kepler-10b to 15%. With a mass of 3.33 ± 0.49 Mearth and an updated radius of 1.47+0.03-0.02 R, Kepler-10b has a density of 5.8 ± 0.8 g cm-3, very close to the value -0.02 predicted by models with the same internal structure and composition as the Earth. We were also able to determine a mass for the 45-day period planet Kepler-10c, with an even better precision of 11%. With a mass of 17.2 ± 1.9 Mearth and radius of 2.35+0.09-0.04 R, -0.04 Kepler-10c has a density of 7.1 ± 1.0 g cm-3. Kepler-10c appears to be the first strong evidence of a class of more massive solid planets with longer orbital periods.

Keywords
planetary systems - stars: individual (Kepler-10 KOI-072 KIC 11904151) - stars: statistics - techniques: photometric - techniques: spectroscopic

The Astrophysical Journal
Volume 789, Number 2, Page 154_1
2014 June

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Instituto de Astrof├şsica e Ci├¬ncias do Espa├žo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa Funda├ž├úo para a Ci├¬ncia e a Tecnologia
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