Rossiter--McLaughlin models and their effect on estimates of stellar rotation, illustrated using six WASP systems

D. J. A. Brown; A. H. M. J. Triaud; A. P. Doyle; M. Gillon; M. Lendl; D. R. Anderson; A. Collier Cameron; G. Hébrard; C. Hellier; C. Lovis; P. F. L. Maxted; F. Pepe; D. Pollacco; D. Queloz; B. Smalley

doi:10.1093/mnras/stw2316

paper

Rossiter--McLaughlin models and their effect on estimates of stellar rotation, illustrated using six WASP systems

arXiv:1610.00600 · doi:10.1093/mnras/stw2316

Abstract

We present new measurements of the projected spin--orbit angle $λ$ for six WASP hot Jupiters, four of which are new to the literature (WASP-61, -62, -76, and -78), and two of which are new analyses of previously measured systems using new data (WASP-71, and -79). We use three different models based on two different techniques: radial velocity measurements of the Rossiter--McLaughlin effect, and Doppler tomography. Our comparison of the different models reveals that they produce projected stellar rotation velocities ( $v sin I_{s}$ ) measurements often in disagreement with each other and with estimates obtained from spectral line broadening. The Boué model for the Rossiter--McLaughlin effect consistently underestimates the value of $v sin I_{s}$ compared to the Hirano model. Although $v sin I_{s}$ differed, the effect on $λ$ was small for our sample, with all three methods producing values in agreement with each other. Using Doppler tomography, we find that WASP-61\,b ( $λ = 4^{\circ} . 0_{- 18.4}^{+ 17.1}$ ), WASP-71\,b ( $λ = - 1^{\circ} . 9_{- 7.5}^{+ 7.1}$ ), and WASP-78\,b ( $λ = - 6^{\circ} .4 \pm 5.9$ ) are aligned. WASP-62\,b ( $λ = 1 9^{\circ} . 4_{- 4.9}^{+ 5.1}$ ) is found to be slightly misaligned, while WASP-79\,b ( $λ = - 9 5^{\circ} . 2_{- 1.0}^{+ 0.9}$ ) is confirmed to be strongly misaligned and has a retrograde orbit. We explore a range of possibilities for the orbit of WASP-76\,b, finding that the orbit is likely to be strongly misaligned in the positive $λ$ direction.

arXiv comment33 pages. Accepted for publication in MNRAS

Rossiter--McLaughlin models and their effect on estimates of stellar rotation, illustrated using six WASP systems

Abstract

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