First Evidence of a Retrograde Orbit of a Transiting Exoplanet HAT-P-7b
Abstract
We present the first evidence of a retrograde orbit of a transiting exoplanet HAT-P-7b. The discovery is based on a measurement of the Rossiter-McLaughlin effect with the Subaru HDS during a transit of HAT-P-7b, which occurred on 2008 May 30 UT. Our best-fit model shows that the spin-orbit alignment angle of this planet is λ = -132.6°<small>+10.5°</small><small>-16.3°</small>. The existence of such a retrograde planet has been predicted by recent planetary migration models that consider planet-planet scattering processes, or Kozai migration. Our finding provides an important milestone that supports such dynamic migration theories.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- October 2009
- DOI:
- 10.1093/pasj/61.5.L35
- arXiv:
- arXiv:0908.1673
- Bibcode:
- 2009PASJ...61L..35N
- Keywords:
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- stars: planetary systems: individual (HAT-P-7);
- stars: rotation;
- techniques: radial velocities;
- techniques: spectroscopic;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- PASJ Letters, in press [13 pages]