2008/06/25 by William D. Cochran, Seth Redfield, Michael Endl +2
Physics and Astronomy · #Astro and Planetary Science #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/591317
4 pages, 1 figure, Ap.J. Letters in press
arxiv created 2008/06/25 · openalex publication_date 2008/07/18 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04
We present high-precision radial velocity observations of HD 17156 during a transit of its eccentric Jovian planet. In these data, we detect the Rossiter-McLaughlin effect, which is an apparent perturbation in the velocity of the star due to the progressive occultation of part of the rotating stellar photosphere by the transiting planet. This system had previously been reported by Narita et al. in 2008 to exhibit a λ = 62°± 25° misalignment of the projected planetary orbital axis and the stellar rotation axis. We model our data, along with the Narita et al. data, and obtain λ = 9.4°± 9.3° for the combined data set. We thus conclude that the planetary orbital axis is actually very well aligned with the stellar rotation axis.