Spin-Orbit Alignment of the TrES-4 Transiting Planetary System and Possible Additional Radial-Velocity Variation
Author(s)Narita, Norio; Sato, Bunei; Hirano, Teruyuki; Winn, Joshua Nathan; Aoki, Wako; Tamura, Motohide; ... Show more Show less
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We report new radial velocities of the TrES-4 transiting planetary system, including observations of a full transit, with the High Dispersion Spectrograph of the Subaru 8.2m telescope. Modeling of the Rossiter-McLaughlin effect indicates that TrES-4b has closely aligned orbital and stellar spin axes, with [lambda]=6.3[degrees]±4.7[degrees]. The close spin-orbit alignment angle of TrES-4b seems to argue against a migration history involving planet-planet scattering or Kozai cycles, although there are two nearby faint stars that could be binary companion candidates. Comparison of our out-of-transit data from 4 different runs suggest that the star exhibits radial velocity variability of 20 m s[superscript −1] in excess of a single Keplerian orbit. Although the cause of the excess radial velocity variability is unknown, we discuss various possibilities including systematic measurement errors, starspots or other intrinsic motions, and additional companions besides the transiting planet.
DepartmentMassachusetts Institute of Technology. Department of Physics; MIT Kavli Institute for Astrophysics and Space Research
Publications of the Astronomical Society of Japan
Astronomical Society of Japan
Narita, Norio, et al. "Spin-Orbit Alignment of the Tres-4 Transiting Planetary System and Possible Additional Radial-Velocity Variation." Publications of the Astronomical Society of Japan 62 3 (2010): 653-60.
Author's final manuscript