Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System
Abstract
We determine the stellar, planetary, and orbital properties of the transiting planetary system HD 209458, through a joint analysis of high-precision radial velocities, photometry, and timing of the secondary eclipse. Of primary interest is the strong detection of the Rossiter-McLaughlin effect, the alteration of photospheric line profiles that occurs because the planet occults part of the rotating surface of the star. We develop a new technique for modeling this effect, and use it to determine the inclination of the planetary orbit relative to the apparent stellar equator [lambda = (-4.4 +/- 1.4) degrees], and the line-of-sight rotation speed of the star [v*sin(I) = (4.70 +/- 0.16) km/s]. The uncertainty in these quantities has been reduced by an order of magnitude relative to the pioneering measurements by Queloz and collaborators. The small but nonzero misalignment is probably a relic of the planet formation epoch, because the expected timescale for tidal coplanarization is larger than the age of the star. Our determination of v*sin(I) is a rare case in which rotational line broadening has been isolated from other broadening mechanisms.
Keywords
Cite
@article{arxiv.astro-ph/0504555,
title = {Measurement of Spin-Orbit Alignment in an Extrasolar Planetary System},
author = {Joshua N. Winn and Robert W. Noyes and Matthew J. Holman and David Charbonneau and Yasuhiro Ohta and Atsushi Taruya and Yasushi Suto and Norio Narita and Edwin L. Turner and John A. Johnson and Geoffrey W. Marcy and R. Paul Butler and Steven S. Vogt},
journal= {arXiv preprint arXiv:astro-ph/0504555},
year = {2011}
}
Comments
21 pages, 6 figures. To match the version accepted by ApJ. Errors have been corrected in Table 1. (In previous versions, some confidence limits were mistakenly 80% rather than 90% limits.)