We report on observations of the Rossiter-McLaughlin (RM) effect for the XO-3 exoplanetary system. The RM effect for the system was previously measured by two different groups, but their results were statistically inconsistent. To obtain a decisive result, we observed two full transits of XO-3b with the Subaru 8.2-m telescope. By modeling these data with a new and more accurate analytic formula for the RM effect, we found the projected spin-orbit angle to be λ = 37.°3±3.°0, in good agreement with a previous finding by Winn et al. (2009 ApJ, 700, 302). In addition, an offset of ∼l22ms -1 was observed between the two transit datasets. This offset could be a signal of a third body in the XO-3 system, a possibility that should be checked with future observations. We also attempted to search for a possible signature of the stellar differential rotation in the RM data for the first time, and put weak upper limits on the differential rotation parameters.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
- Stars: planetary systems: pindividual (XO-3)
- Stars: rotation
- Techniques: radial velocities
- Techniques: spectroscopic