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

TL;DR

This study measures the spin-orbit alignment angles of three hot Jupiter systems using spectroscopic techniques, providing insights into their orbital configurations and contributing to the understanding of planetary system evolution.

Contribution

It offers new measurements of lambda for WASP-32 and WASP-38 with improved precision, and presents a loosely constrained measurement for HAT-P-27/WASP-40, expanding the sample of known alignments.

Findings

WASP-32 is aligned with lambda ≈ 10.5°

WASP-38 is aligned with lambda ≈ 7.5°

HAT-P-27/WASP-40 has a loosely constrained lambda around 24°

Abstract

We present measurements of the spin-orbit alignment angle, lambda, for the hot Jupiter systems WASP-32, WASP-38, and HAT-P-27/WASP-40, based on data obtained using the HARPS spectrograph. We analyse 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 lambda = 10.5 +6.4 -6.5 degrees obtained through tomography, and that WASP-38 (T_eff = 6180 +40 -60 K) is also aligned, with tomographic analysis yielding lambda = 7.5 +4.7 -6.1 degrees. This latter result provides an order of magnitude improvement in the uncertainty in lambda compared to the previous analysis of Simpson et al. (2011). We are only able to loosely constrain the angle for HAT-P-27/WASP-40 (T_eff = 5190 +160 -170 K) to lambda = 24.2 +76.0 -44.5 degrees, owing to the poor signal-to-noise of our data. We consider this result a non-detection under a slightly updated version of the alignment test of Brown et al. (2012). 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.