XO-3b spin-orbit misalignment not as bad as thought.

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XO-3b spin-orbit misalignment not as bad as thought.

Post by Sirius_Alpha on 22nd February 2009, 9:15 pm

The Spin-Orbit Misalignment of the XO-3 Exoplanetary System

Abstract wrote:We present photometric and spectroscopic observations of the 2009 Feb. 2 transit of the exoplanet XO-3b. The new data show conclusively that the planetary orbital axis and stellar rotation axis are misaligned. We thereby confirm the previous finding by Hebrard and coworkers, although we find a significantly smaller angle (37.3 +/- 3.7 deg) between the sky projections of the two axes. XO-3b is the first exoplanet known to have a highly inclined orbit relative to the equatorial plane of its parent star, and as such it may fulfill the predictions of some scenarios for the migration of massive planets into close-in orbits. We revisit the statistical analysis of spin-orbit alignment in hot-Jupiter systems. Assuming the stellar obliquities to be drawn from a Rayleigh distribution, we find the mode of the distribution to be 13^{+5}_{-2} deg. It remains the case that a model representing two different migration channels--in which some planets are drawn from a perfectly-aligned distribution and the rest are drawn from an isotropic distribution--is favored over a single Rayleigh distribution, but with reduced significance.

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