RESEARCH
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Spin-orbit inclinations of the exoplanetary systems HAT-P-8b, HAT-P-9b, HAT-P-16b, and HAT-P-23b

C. Moutou, R. F. DÝaz, S. Udry, G. HÚbrard, F. Bouchy, A. Santerne, D. Ehrenreich, L. Arnold, I. Boisse, X. Bonfils, X. Delfosse, A. Eggenberger, T. Forveille, A.-M. Lagrange, C. Lovis, P. Martinez, F. Pepe, C. Perrier, D. Queloz, N. C. Santos, D. SÚgransan, D. Toublanc, J. P. Troncin, M. Vanhuysse, A. Vidal-Madjar

Abstract
We report the measurement of the spin-orbit angle of the extra-solar planets HAT-P-8 b, HAT-P-9 b, HAT-P-16 b, and HAT-P-23 b, based on spectroscopic observations performed at the Observatoire de Haute-Provence with the SOPHIE spectrograph on the 1.93-m telescope. Radial velocity measurements of the Rossiter-McLaughlin effect show the detection of an apparent prograde, aligned orbit for all systems. The projected spin-orbit angles are found to be λ = -17°+9.2-11.5, -16° ± 8°, –10° ± 16°, and +15° ± 22° for HAT-P-8, HAT-P-9, HAT-P-16, and HAT-P-23, respectively, with corresponding projected rotational velocities of 14.5±0.8, 12.5±1.8, 3.9±0.8, and 7.8 ± 1.6 kms-1. These new results increase to 37 the number of accurately measured spin-orbit angles in transiting extrasolar systems. We conclude by drawing a tentative picture of the global behaviour of orbital alignement, involving the complexity and diversity of possible mechanisms.

Keywords
techniques: radial velocities - planet-star interactions - planetary systems

Notes
Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium (program 10A.PNP.CONS).
http://www.encyclopedia.edu

Astronomy and Astrophysics
Volume 533, Number of pages A113_1
2011 September

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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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