Abstract
We present Rossiter-McLaughlin observations of WASP-13b and WASP-32b and determine the sky-projected angle between the normal of the planetary orbit and the stellar rotation axis (λ). WASP-13b and WASP-32b both have prograde orbits and are consistent with alignment with measured sky-projected angles of λ = 8º+13-12 and λ = -2º+17-19, respectively. Both WASP-13 and WASP-32 have Teff < 6250 K, and therefore, these systems support the general trend that aligned planetary systems are preferentially found orbiting cool host stars. A Lomb-Scargle periodogram analysis was carried out on archival SuperWASP data for both systems. A statistically significant stellar rotation period detection (above 99.9 per cent confidence) was identified for the WASP-32 system with Prot = 11.6 ± 1.0 days. This rotation period is in agreement with the predicted stellar rotation period calculated from the stellar radius, R*, and vsin i if a stellar inclination of i* = 90º is assumed. With the determined rotation period, the true 3D angle between the stellar rotation axis and the planetary orbit, ψ, was found to be ψ = 11º ± 14º. We conclude with a discussion on the alignment of systems around cool host stars with Teff < 6150 K by calculating the tidal dissipation time-scale. We find that systems with short tidal dissipation time-scales are preferentially aligned and systems with long tidal dissipation time-scales have a broad range of obliquities.
| Original language | English |
|---|---|
| Pages (from-to) | 3392-3401 |
| Number of pages | 10 |
| Journal | Royal Astronomical Society. Monthly Notices |
| Volume | 440 |
| Early online date | 17 Apr 2014 |
| DOIs | |
| Publication status | Published - 1 Jun 2014 |
Keywords
- techniques: photometric
- techniques: radial velocities
- stars: individual: WASP-13
- stars: individual: WASP-32
- planetary systems