Analysis of spin-orbit alignment in the WASP-32, WASP-38, and HAT-p-27/WASP-40 systems

D. J. A. Brown, A. Collier Cameron, R. F. Díaz, A. P. Doyle, M. Gillon, M. Lendl, B. Smalley, A. H. M. J. Triaud, D. R. Anderson, B. Enoch, C. Hellier, P. F. L. Maxted, G. R. M. Miller, D. Pollacco, D. Queloz, I. Boisse, G. Hébrard

Abstract
We present measurements of the spin–orbit alignment angle, λ, for the hot Jupiter systems WASP-32, WASP-38, and HAT-P-27/WASP-40, based on data obtained using the HARPS spectrograph. We analyze the Rossiter–McLaughlin effect for all three systems and also carry out Doppler tomography for WASP-32 and WASP-38. We find that WASP-32 (T_eff = 6140⁺⁹⁰_-100 K) is aligned, with an alignment angle of λ = 10°.5^+6.4_-6.5 obtained through tomography, and that WASP-38 (T_eff = 6180⁺⁴⁰_-60 K) is also aligned, with tomographic analysis yielding λ = 7°.5^+4.7_-6.1. The latter result provides an order-of-magnitude improvement in the uncertainty in λ compared to the previous analysis of Simpson et al. We are only able to loosely constrain the angle for HAT-P-27/WASP-40 (T_eff = 5190⁺¹⁶⁰_-170 K) to λ = 24°.2^+76.0_-44.5, owing to the poor signal-to-noise ratio of our data. We consider this result a non-detection under a slightly updated version of the alignment test of Brown et al. We place our results in the context of the full sample of spin–orbit alignment measurements, finding that they provide further support for previously established trends.

Notes
Based on observations (under proposal 087.C-0649) made using the HARPS High Resolution Échelle Spectrograph mounted on the ESO 3.6 m at the ESO La Silla observatory.

The Astrophysical Journal
Volume 760, Page 139_1
December 2012

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