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Teruyuki Hirano, Norio Narita, Bun’ei Sato, Joshua N. Winn, Wako Aoki, Motohide Tamura, Atsushi Taruya, Yasushi Suto, Further Observations of the Tilted Planet XO-3: A New Determination of Spin–Orbit Misalignment, and Limits on Differential Rotation, Publications of the Astronomical Society of Japan, Volume 63, Issue 6, 25 December 2011, Pages L57–L61, https://doi.org/10.1093/pasj/63.6.L57
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Abstract
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 |${\lambda}$||$=$| 37|$^\circ\!\!\!.$|3|$\ \pm\ $|3|$^\circ\!\!\!.$|0, in good agreement with a previous finding by Winn et al. (2009) (2009 ApJ, 700, 302). In addition, an offset of |$\sim\ $|22 m s|$^{-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.
