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

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 = 10fdg5 + 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 = 7fdg5 + 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 = 24fdg2 + 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. 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.