NOAO >   Observing Info >   Approved Programs >   2011A-0557

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Proposal Information for 2011A-0557


PI: Bo Ma, boma@astro.ufl.edu
Address: 211 Bryant Space Science Center, Gainesville

CoI: Jian Ge

Title: Detecting Rossiter-McLaughlin effect around two transiting exoplanet using EXPERT

Abstract: To date about 90 hot jupiters with periods \le10 days has been detected around solar like stars. While it is generally accepted that close-orbiting gas-giant planets do not form in-situ, their previous evolution is still mysterious. Several processes can affect the planet's eccentricity and semi-major axis. The slowly inward migration caused by the interaction between the giant planet and the disk will have a negligible effect on the alignment between the stellar spin axis and the planetary orbital axis, maintaining its nearly circular orbit that is co-planar with the disk (Lin et al. 1996). Alternative migration mechanism such as planet-planet scattering (Rasio & Ford 1996) and Kozai effect (Holman et al. 1997) will cause significant axis misalignment. Therefore, measurements of the planet orbital inclinations relative to the stellar equator offers diagnostic of the original migration process. The Rossiter-McLaughlin (R-M) effect offers a unique way to assess quantitatively the spin-orbit alignment of a planetary system by measuring the Doppler effect of the star's light during a planetary transit. As the planet blocks receding portion of a rotating star´┐Ż surface, the spectrum from the unobscured surface has a net Doppler shift toward shorter wavelengths, and vice versa for blocking the approaching portion of the star (Queloz et al. 2000). To date, the R-M effect has been measured in 27 stars, which show there is a very wide distribution of the obit obliquity angle (lambda). More measurements of the R-M effect will play an important role in constraining planetary migration models by studying the statistical distribution of spin-orbit alignment angles among different type stars. Here we propose to observe the R-M effect in another 2 transiting planets around relatively bright stars (V<10.5) to search for the R-M effect using the EXPERT RV mode. Results from this proposal and future observations of more transiting planets would contribute significantly to constrain the giant planet migration theory.


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