Stellar Spin–Orbit Alignment for Kepler-9, a Multi-transiting Planetary System with Two Outer Planets Near 2:1 Resonance

Creators: Wang, Songhu; Addison, Brett; Fischer, Debra A.; Brewer, John M.; Isaacson, Howard; Howard, Andrew W.; Laughlin, Gregory

Abstract

We present spectroscopic measurements of the Rossiter–McLaughlin effect for the planet b of the Kepler-9 multi-transiting planetary system. The resulting sky-projected spin–orbit angle is λ = −13° ± 16°, which favors an aligned system and strongly disfavors highly misaligned, polar, and retrograde orbits. Including Kepler-9, there are now a total of four Rossiter–McLaughlin effect measurements for multiplanet systems, all of which are consistent with spin–orbit alignment.

Additional Information

© 2018. The American Astronomical Society. Received 2017 September 22; revised 2017 December 7; accepted 2017 December 17; published 2018 January 19. We are thankful to the referee Simon Albrecht for providing a thorough review that greatly improved the manuscript. We would also like to thank Dong Lai, Amaury Triaud, Christopher Spalding, Smadar Naoz, Douglas Lin, Yasunori Hori, and Hui-Gen Liu for useful discussions, as well as Yutong Wu, Xiaojia Zhang, and Dong-Hong Wu for improving the quality of the figures. S.W. acknowledges the Heising-Simons Foundation for their generous support. Finally, the authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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Submitted - 1712.06409.pdf

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