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arXiv · 0806.1734

Measurement of the Spin-Orbit Angle of Exoplanet HAT-P-1b

John A. Johnson·Joshua N. Winn·Norio Narita·Keigo Enya·Peter K. G. Williams·Geoffrey W. Marcy·Bun'ei Sato·Yasuhiro Ohta·Atsushi Taruya·Yasushi Suto·Edwin L. Turner·Gaspar Bakos·R. Paul Butler·Steven S. Vogt·Wako Aoki·Motohide Tamura·Toru Yamada·Yuzuru Yoshii·Marton Hidas
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Abstract

We present new spectroscopic and photometric observations of the HAT-P-1 planetary system. Spectra obtained during three transits exhibit the Rossiter-McLaughlin effect, allowing us to measure the angle between the sky projections of the stellar spin axis and orbit normal, \lambda = 3.7 +/- 2.1 degrees. The small value of \lambda for this and other systems suggests that the dominant planet migration mechanism preserves spin-orbit alignment. Using two new transit light curves, we refine the transit ephemeris and reduce the uncertainty in the orbital period by an order of magnitude. We find a upper limit on the orbital eccentricity of 0.067, with 99% confidence, by combining our new radial-velocity measurements with those obtained previously.

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John A. Johnson, Joshua N. Winn, Norio Narita, Keigo Enya, Peter K. G. Williams, Geoffrey W. Marcy, Bun'ei Sato, Yasuhiro Ohta, Atsushi Taruya, Yasushi Suto, Edwin L. Turner, Gaspar Bakos, R. Paul Butler, Steven S. Vogt, Wako Aoki, Motohide Tamura, Toru Yamada, Yuzuru Yoshii, Marton Hidas. 2008-06-10. Measurement of the Spin-Orbit Angle of Exoplanet HAT-P-1b. https://doi.org/10.1086/591078

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