TWO UPPER LIMITS ON THE ROSSITER-MCLAUGHLIN EFFECT, WITH DIFFERING IMPLICATIONS: WASP-1 HAS A HIGH OBLIQUITY AND WASP-2 IS INDETERMINATE
Author(s)
Albrecht, Simon H.
Winn, Joshua Nathan
Johnson, John Asher
Butler, R. Paul
Crane, Jeffrey D.
Shectman, Stephen A.
Thompson, Ian B.
Narita, Norio
Sato, Bun'ei
Hirano, Teruyuki
Date Issued
September 2011
Journal
Astrophysical Journal
Publisher
Institute of Physics Publishing
Citation
Albrecht, Simon et al. “TWO UPPER LIMITS ON THE ROSSITER-MCLAUGHLIN EFFECT, WITH DIFFERING IMPLICATIONS: WASP-1 HAS A HIGH OBLIQUITY AND WASP-2 IS INDETERMINATE.” The Astrophysical Journal 738.1 (2011): 50. Web.
Version
Author's final manuscript
Abstract
We present precise radial-velocity (RV) measurements of WASP-1 and WASP-2 throughout transits of their giant planets. Our goal was to detect the Rossiter-McLaughlin (RM) effect, the anomalous RV observed during eclipses of rotating stars, which can be used to study the obliquities of planet-hosting stars. For WASP-1, a weak signal of a prograde orbit was detected with [almost equal to]2omega confidence, and for WASP-2 no signal was detected. The resulting upper bounds on the RM amplitude have different implications for these two systems because of the contrasting transit geometries and the stellar types. Because WASP-1 is an F7V star, and such stars are typically rapid rotators, the most probable reason for the suppression of the RM effect is that the star is viewed nearly pole-on. This implies that the WASP-1 star has a high obliquity with respect to the edge-on planetary orbit. Because WASP-2 is a K1V star, and is expected to be a slow rotator, no firm conclusion can be drawn about the stellar obliquity. Our data and our analysis contradict an earlier claim that WASP-2b has a retrograde orbit, thereby revoking this system's status as an exception to the pattern that cool stars have low obliquities.
MIT Department
Massachusetts Institute of Technology. Department of Physics
MIT Kavli Institute for Astrophysics and Space Research
Terms of Use
Creative Commons Attribution-Noncommercial-Share Alike 3.0
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1088/0004-637x/738/1/50
