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

Abstract

We present new measurements of the projected spin--orbit angle $\lambda$ 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 ($v\sin I_{\mathrm{s}}$) 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 $v\sin I_{\mathrm{s}}$ compared to the Hirano model. Although $v\sin I_s$ differed, the effect on $\lambda$ 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 ($\lambda =4^{\circ }.0_{-18.4}^{+17.1}$), WASP-71\,b ($\lambda =-1^{\circ }.9_{-7.5}^{+7.1}$), and WASP-78\,b ($\lambda =-6^{\circ }.4\pm 5.9$) are aligned. WASP-62\,b ($\lambda =19^{\circ }.4_{-4.9}^{+5.1}$) is found to be slightly misaligned, while WASP-79\,b ($\lambda =-95^{\circ }.2_{-1.0}^{+0.9}$) 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 $\lambda$ direction.

33 pages. Accepted for publication in MNRAS

References in corpus (16)

• Efficient identification of exoplanetary transit candidates from SuperWASP light curves
• Determining stellar macroturbulence using asteroseismic rotational velocities from Kepler
• WASP-3b: a strongly-irradiated transiting gas-giant planet
• Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars
• WASP-42 b and WASP-49 b: two new transiting sub-Jupiters
• Misaligned Protoplanetary Disks in a Young Binary System
• The spin axes orbital alignment of both stars within the eclipsing binary system V1143Cyg using the Rossiter-McLaughlin effect
• On the tidal origin of hot Jupiter stellar obliquity trends
• Predicting Photometric and Spectroscopic Signatures of Rings around Transiting Extrasolar Planets
• WASP-78b and WASP-79b: Two highly-bloated hot Jupiter-mass exoplanets orbiting F-type stars in Eridanus
• The GAPS Programme with HARPS-N at TNG. III: The retrograde orbit of HAT-P-18b
• Discrepancies between isochrone fitting and gyrochronology for exoplanet host stars?
• The BANANA project. V. Misaligned and precessing stellar rotation axes in CV Velorum
• Analysis of spin-orbit alignment in the WASP-32, WASP-38, and HAT-P-27/WASP-40 systems
• WASP-117b: a 10-day-period Saturn in an eccentric and misaligned orbit
• Spin-Orbit Alignment For 110-Day-Period KOI368.01 From Gravity Darkening

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