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WASP-131 b with ESPRESSO – I. A bloated sub-Saturn on a polar orbit around a differentially rotating solar-type star

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posted on 2024-04-22, 10:37 authored by L Doyle, HM Cegla, DR Anderson, M Lendl, V Bourrier, E Bryant, J Vines, R Allart, D Bayliss, MR Burleigh, N Buchschacher, SL Casewell, F Hawthorn, JS Jenkins, M Lafarga, M Moyano, A Psaridi, N Roguet-Kern, D Sosnowska, P Wheatley

In this paper, we present observations of two high-resolution transit data sets obtained with ESPRESSO of the bloated sub-Saturn planet WASP-131 b. We have simultaneous photometric observations with NGTS and EulerCam. In addition, we utilized photometric light curves from TESS, WASP, EulerCam, and TRAPPIST of multiple transits to fit for the planetary parameters and update the ephemeris. We spatially resolve the stellar surface of WASP-131 utilizing the Reloaded Rossiter McLaughlin technique to search for centre-to-limb convective variations, stellar differential rotation, and to determine the star–planet obliquity for the first time. We find WASP-131 is misaligned on a nearly retrograde orbit with a projected obliquity of $\lambda = 162.4\substack{+1.3 \\ -1.2}^{\circ }$ . In addition, we determined a stellar differential rotation shear of α = 0.61 ± 0.06 and disentangled the stellar inclination ($i_* = 40.9\substack{+13.3 \\ -8.5}^{\circ }$ ) from the projected rotational velocity, resulting in an equatorial velocity of $v_{\rm {eq}} = 7.7\substack{+1.5 \\ -1.3}$ km s−1. In turn, we determined the true 3D obliquity of $\psi = 123.7\substack{+12.8 \\ -8.0}^{\circ }$ , meaning the planet is on a perpendicular/polar orbit. Therefore, we explored possible mechanisms for the planetary system’s formation and evolution. Finally, we searched for centre-to-limb convective variations where there was a null detection, indicating that centre-to-limb convective variations are not prominent in this star or are hidden within red noise.

History

Author affiliation

College of Science & Engineering/Physics & Astronomy

Version

  • VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Volume

522

Issue

3

Pagination

4499 - 4514

Publisher

Oxford University Press (OUP)

issn

0035-8711

eissn

1365-2966

Copyright date

2023

Available date

2024-04-22

Language

en

Deposited by

Dr Matthew Burleigh

Deposit date

2024-04-17

Data Access Statement

The TESS data are available from the NASA MAST portal and the ESO ESPRESSO data are public from the ESO data archive. CORALIE radial velocities are available through the discovery paper Hellier et al. (2017). The remaining photometry (NGTS, EulerCam etc.) is available as supplementary material online with this paper.

Rights Retention Statement

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