CONFIRMATION OF A RETROGRADE ORBIT FOR EXOPLANET WASP-17b
- Research School of Astronomy and Astrophysics, Australian National University, Mt Stromlo Observatory, Cotter Rd, Weston Creek, ACT 2611 (Australia)
- Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
We present high-precision radial velocity observations of WASP-17 throughout the transit of its close-in giant planet, using the MIKE spectrograph on the 6.5 m Magellan Telescope at Las Campanas Observatory. By modeling the Rossiter-McLaughlin effect, we find the sky-projected spin-orbit angle to be {lambda} = 167.4 {+-} 11.2 deg. This independently confirms the previous finding that WASP-17b is on a retrograde orbit, suggesting it underwent migration via a mechanism other than just the gravitational interaction between the planet and the disk. Interestingly, our result for {lambda} differs by 45 {+-} 13 deg from the previously announced value, and we also find that the spectroscopic transit occurs 15 {+-} 5 minutes earlier than expected, based on the published ephemeris. The discrepancy in the ephemeris highlights the need for contemporaneous spectroscopic and photometric transit observations whenever possible.
- OSTI ID:
- 21452729
- Journal Information:
- Astrophysical Journal Letters, Vol. 722, Issue 2; Other Information: DOI: 10.1088/2041-8205/722/2/L224; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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