Joshua N. Winn et al 2009 ApJ 703 L99 doi:10.1088/0004-637X/703/2/L99
HAT-P-7: A RETROGRADE OR POLAR ORBIT, AND A THIRD BODY
FREE ISSUEJoshua N. Winn1, John Asher Johnson2,7, Simon Albrecht1, Andrew W. Howard3,4,8, Geoffrey W. Marcy3, Ian J. Crossfield5 and Matthew J. Holman6
Show affiliationsWe show that the exoplanet HAT-P-7b has an extremely tilted orbit, with a true angle of at least 86° with respect to its parent star's equatorial plane, and a strong possibility of retrograde motion. We also report evidence for an additional planet or companion star. The evidence for the unparalleled orbit and the third body is based on precise observations of the star's apparent radial velocity (RV). The anomalous RV due to rotation (the Rossiter-McLaughlin effect) was found to be a blueshift during the first half of the transit and a redshift during the second half, an inversion of the usual pattern, implying that the angle between the sky-projected orbital and stellar angular momentum vectors is 182
5 ± 94. The third body is implicated by excess RV variation of the host star over 2 yr. Some possible explanations for the tilted orbit of HAT-P-7b are a close encounter with another planet, the Kozai effect, and resonant capture by an inward-migrating outer planet.
- Keywords
planetary systems; planetary systems: formation; stars: individual (HAT-P-7); stars: rotation
- PACS
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97.82.Fs Substellar companions; planets
97.82.Cp Photometric and spectroscopic detection; coronographic detection; interferometric detection
97.10.Wn Proper motions and radial velocities (line-of-sight velocities); space motions
97.82.Jw Infrared excess; debris disks; protoplanetary disks; exo-zodiacal dust
- Subjects
- Dates
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Issue 2 (2009 October 1)
Received 2009 August 12, accepted for publication 2009 August 21
Published 2009 September 8
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HAT-P-7: A Retrograde or Polar Orbit, and a Third Body
Joshua N. Winn et al 2009 ApJ 703 L99
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