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A LOW STELLAR OBLIQUITY FOR WASP-47, A COMPACT MULTIPLANET SYSTEM WITH A HOT JUPITER AND AN ULTRA-SHORT PERIOD PLANET

2015/09/17 by Roberto Sanchis-Ojeda, Joshua N. Winn, Fei Dai +12 · 50 citations
Physics and Astronomy · #Acoustics #Astrobiology #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Exoplanet #Hot Jupiter #Jupiter (rocket family) #Orbital period #Period (music) #Physics #Planet #Space exploration #Stars #Stellar, planetary, and galactic studies #astro-ph.EP

paper · pdf · doi:10.1088/2041-8205/812/1/l11

published in The Astrophysical Journal Letters 812(1), L11 (IOP Publishing) · 5 pages, 2 figures, Accepted for publication on ApJL, comments welcome

arxiv created 2015/09/17 · openalex publication_date 2015/10/07 · arxiv updated 2015/10/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

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° ± 24°. 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 ◦ , remains the only clear counterexample.

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