Publication Date:
2014-04-19
Description:
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 (). WASP-13b and WASP-32b both have prograde orbits and are consistent with alignment with measured sky-projected angles of $\lambda =8{^{\circ }}^{+13}_{-12}$ and $\lambda =-2{^{\circ }}^{+17}_{-19}$, respectively. Both WASP-13 and WASP-32 have T eff 〈 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 P rot = 11.6 ± 1.0 days. This rotation period is in agreement with the predicted stellar rotation period calculated from the stellar radius, R * , and v sin i if a stellar inclination of i * = 90° is assumed. With the determined rotation period, the true 3D angle between the stellar rotation axis and the planetary orbit, , was found to be = 11° ± 14°. We conclude with a discussion on the alignment of systems around cool host stars with T eff 〈 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.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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