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arXiv · 1509.05337

A low stellar obliquity for WASP-47, a compact multiplanet system with a hot Jupiter and an ultra-short period planet

Roberto Sanchis-Ojeda·Joshua N. Winn·Fei Dai·Andrew W. Howard·Howard Isaacson·Geoffrey W. Marcy·Erik Petigura·Evan Sinukoff·Lauren Weiss·Simon Albrecht·Teruyuki Hirano·Leslie Rogers
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Abstract

We have detected the Rossiter-Mclaughlin effect during a transit of WASP-47b, the only known hot Jupiter with close planetary companions. By combining our spectroscopic observations with Kepler photometry, we show that the projected stellar obliquity is $λ= 0^\circ \pm 24^\circ$. We can firmly exclude a retrograde orbit for WASP-47b, and rule out strongly misaligned prograde orbits. Low obliquities have also been found for most of the other compact multiplanet systems that have been investigated. The Kepler-56 system, with two close-in gas giants transiting their subgiant host star with an obliquity of at least 45$^\circ$, remains the only clear counterexample.

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Roberto Sanchis-Ojeda, Joshua N. Winn, Fei Dai, Andrew W. Howard, Howard Isaacson, Geoffrey W. Marcy, Erik Petigura, Evan Sinukoff, Lauren Weiss, Simon Albrecht, Teruyuki Hirano, Leslie Rogers. 2015-09-17. A low stellar obliquity for WASP-47, a compact multiplanet system with a hot Jupiter and an ultra-short period planet. https://doi.org/10.1088/2041-8205%2F812%2F1%2Fl11

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