Journal Article

The spin-orbit angles of the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b from Rossiter–McLaughlin observations*

E. K. Simpson, D. Pollacco, A. Collier Cameron, G. Hébrard, D. R. Anderson, S. C. C. Barros, I. Boisse, F. Bouchy, F. Faedi, M. Gillon, L. Hebb, F. P. Keenan, G. R. M. Miller, C. Moutou, D. Queloz, I. Skillen, P. Sorensen, H. C. Stempels, A. Triaud, C. A. Watson and P. A. Wilson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 4, pages 3023-3035
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18603.x
The spin-orbit angles of the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b from Rossiter–McLaughlin observations*

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We present observations of the Rossiter–McLaughlin effect for the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b, and deduce the orientations of the planetary orbits with respect to the host stars’ rotation axes. The planets WASP-24b, WASP-38b and HAT-P-8b appear to move in prograde orbits and be well aligned, having sky-projected spin-orbit angles consistent with zero: λ=−4°.7 ± 4°.0, 15°+33−43 and , respectively. The host stars have Teff < 6250 K and conform with the trend of cooler stars having low obliquities. WASP-38b is a massive planet on a moderately long period, eccentric orbit so may be expected to have a misaligned orbit given the high obliquities measured in similar systems. However, we find no evidence for a large spin-orbit angle. By contrast, WASP-1b joins the growing number of misaligned systems and has an almost polar orbit, λ=. It is neither very massive, eccentric nor orbiting a hot host star, and therefore does not share the properties of many other misaligned systems.

Keywords: techniques: radial velocities; stars: individual: WASP-1; stars: individual: WASP-24; stars: individual: WASP-38; stars: individual: HAT-P-8; planetary systems

Journal Article.  7216 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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