A Low Stellar Obliquity for WASP-47, a Compact Multiplanet System with a Hot Jupiter and an Ultra-short Period Planet
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2015
- DOI:
- 10.1088/2041-8205/812/1/L11
- arXiv:
- arXiv:1509.05337
- Bibcode:
- 2015ApJ...812L..11S
- Keywords:
-
- planet–star interactions;
- planetary systems;
- planets and satellites: formation;
- stars: rotation;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 5 pages, 2 figures, Accepted for publication on ApJL, comments welcome