@article{f606f39ede3c48249a7117d40e14f1de,
title = "SPIN-ORBIT ALIGNMENT of EXOPLANET SYSTEMS: ENSEMBLE ANALYSIS USING ASTEROSEISMOLOGY",
abstract = "The angle ψ between a planet's orbital axis and the spin axis of its parent star is an important diagnostic of planet formation, migration, and tidal evolution. We seek empirical constraints on ψ by measuring the stellar inclination is via asteroseismology for an ensemble of 25 solar-type hosts observed with NASA's Kepler satellite. Our results for is are consistent with alignment at the 2σ level for all stars in the sample, meaning that the system surrounding the red-giant star Kepler-56 remains as the only unambiguous misaligned multiple-planet system detected to date. The availability of a measurement of the projected spin-orbit angle λ for two of the systems allows us to estimate ψ. We find that the orbit of the hot Jupiter HAT-P-7b is likely to be retrograde, (ψ=116.4-14.7+30.2)whereas that of Kepler-25c seems to be well aligned with the stellar spin axis (ψ12.6-11.0+6.7). While the latter result is in apparent contradiction with a statement made previously in the literature that the multi-transiting system Kepler-25 is misaligned, we show that the results are consistent, given the large associated uncertainties. Finally, we perform a hierarchical Bayesian analysis based on the asteroseismic sample in order to recover the underlying distribution of ψ. The ensemble analysis suggests that the directions of the stellar spin and planetary orbital axes are correlated, as conveyed by a tendency of the host stars to display large values of inclination.",
keywords = "asteroseismology, methods: statistical, planetary systems, planets and satellites: general, stars: solar-type, techniques: photometric",
author = "Campante, {T. L.} and Lund, {M. N.} and Kuszlewicz, {J. S.} and Davies, {G. R.} and Chaplin, {W. J.} and S. Albrecht and Winn, {J. N.} and Bedding, {T. R.} and O. Benomar and D. Bossini and R. Handberg and Santos, {A. R.G.} and {Van Eylen}, V. and S. Basu and J. Christensen-Dalsgaard and Elsworth, {Y. P.} and S. Hekker and T. Hirano and D. Huber and C. Karoff and H. Kjeldsen and Lundkvist, {M. S.} and North, {T. S.H.} and {Silva Aguirre}, V. and D. Stello and White, {T. R.}",
note = "Funding Information: This paper includes data collected by the Kepler mission. Funding for the Kepler mission is provided by the NASA Science Mission Directorate. Some of the data presented in this paper were obtained from the Kepler Asteroseismic Science Operations Center (KASOC) database. T.L.C., J.S.K., G.R.D., W.J.C., D.B., Y.P.E., and T.S.H.N. acknowledge the support of the UK Science and Technology Facilities Council (STFC). Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant DNRF106). The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (Grant agreement no.: 267864). The research leading to the presented results has received funding from the European Research Council under the European Community{\textquoteright}s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no. 338251 (StellarAges). Work by J.N.W. was supported by the NASA Origins program (NNX11AG85G). S.B. acknowledges support from NASA grant NNX13AE70G. C.K. and V.S.A. acknowledge the support of the Villum Foundation. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This study has made use of Ren{\'e} Heller{\textquoteright}s Holt–Rossiter–McLaughlin Encyclopaedia. This research made use of the Python package obliquity developed by Timothy Morton and made available at https:// github.com/timothydmorton/obliquity. Publisher Copyright: {\textcopyright} 2016. The American Astronomical Society. All rights reserved..",
year = "2016",
month = mar,
day = "1",
doi = "10.3847/0004-637X/819/1/85",
language = "English (US)",
volume = "819",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "1",
}