Measuring the Spin-Orbit Alignments of Transiting Exoplanetary Systems: The Case for TrES-1 Norio Narita, Keigo Enya, Bun'ei Sato, Yasuhiro Ohta, Joshua N. Winn, Yasushi Suto, Atsushi Taruya, Edwin L. Turner, Wako Aoki, Motohide Tamura, Toru Yamada, Yuzuru Yoshii Formation Models of Close-in Planets How have they migrated to their current position? Planet migration mechanisms and outcomes: Disk-Planet interaction e.g., Lin et al. 1996 Planets gradually migrate inward within their disks small eccentricity and inclination Planet-Planet interaction e.g., Rasio & Ford 1996, Weidenschilling & Marzari 1996 giant planets scatter one another possible large eccentricity and inclination subsequent tidal circularization The Kozai migration in binary systems e.g., Wu & Murray 2003 eccentricity/inclination oscillations induced by separated binary companion Inclination (spin-orbit alignment) is an useful diagnostic The Rossiter-McLaughlin Effect What can we learn from this effect? Misalignment parameter λ Examples of trajectory and corresponding radial velocity anomaly of the RM effect (Gaudi & Winn 2007) The RM effect is: originally discovered in eclipsing binary systems Rossiter 1924, McLaughlin 1924 seen as radial velocity anomaly during a transit dependent on the trajectory of the planet across the stellar disk Ohta et al. 2005, Gimenez 2006, Gaudi & Winn 2007 One can measure the sky-projected angle between the stellar spin axis and the planetary orbital axis λ One can test the planet migration models by measuring the spin-orbit alignments in exoplanetary systems! The Case for TrES-1 Observations simultaneous spectroscopic/photometric observations Subaru 8.2 m telescope at Mauna Kea (Hawaii) MAGNUM 2 m telescope at Haleakala (Maui) observing date: UT 2006 June 21 RV precision: 10 ～ 15 m/s photometric precision: ～ 2mmag Parameters of TrES-1 V = 11.8 (relatively faint) K0V star (small rotational velocity) duration = 150 min i (orbital inclination) ～ 90 deg challenging target for the RM observation orbital phase transit phase -0.5 -0.05 0.05 radial velocity and light curve constraints on λ = 30 ± 21 [deg] (a) See details in Narita et al. (2007) (astro-ph/0702707) best-fitting model (with/without constraint on VsinIs) Future Prospects of Our Project We have demonstrated that the RM effect is detectable for a relatively faint (V～12) target Our TrES-1 result is the first demonstration for a V～12 host star New targets in this category have been discovered We can measure spin-orbit alignments of those targets We plan to conduct further RM observations for newly discovered targets with Subaru/MAGNUM telescopes in 2007 We will present the distribution of spin-orbit alignments of transiting exoplanetary systems Such observational information will allow us to test planet migration models in the near future