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

2011; Oxford University Press; Volume: 414; Issue: 4 Linguagem: Inglês

10.1111/j.1365-2966.2011.18603.x

1365-2966

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, Leslie Hebb, F. P. Keenan, G. R. M. Miller, C. Moutou, D. Queloz, I. Skillen, P. Sørensen, H. C. Stempels, A. H. M. J. Triaud, C. A. Watson, P. A. Wilson,

Astrophysics and Star Formation Studies

We present observations of the Rossiter-McLaughlin effect for the transiting exoplanet systems WASP-1, WASP-24, WASP-38 and HAT-P-8, 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: {\lambda} = -4.7 \pm 4.0{\deg}, {\lambda} = 15 + 33{\deg}/-43{\deg} and {\lambda} = -9.7 +9.0{\deg}/-7.7{\deg}, 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, {\lambda} = -79 +4.5{\deg}/-4.3{\deg}. It is neither very massive, eccentric nor orbiting a hot host star, and therefore does not share the properties of many other misaligned systems.