Simultaneous Subaru/MAGNUM Observations of Extrasolar Planetary Transits

1. 1 / 18 Simultaneous Subaru/MAGNUMObservations of Extrasolar Planetary Transits Norio Narita (U. Tokyo, JSPS Fellow, Japan) Collaborators Y. Ohta, A. Taruya, Y. Suto, (U. Tokyo) B. Sato, M. Tamura, T. Yamada, W Aoki, (NAOJ) K. Enya, (JAXA) J. N. Winn, (MIT) E. L. Turner, (Princeton)

2. 2 / 18 Contents • Two Japanese Telescopes in Hawaii • Research Projects • Transmission Spectroscopy • Measurements of the Rossiter effect • Previous and Ongoing Work • Sensitivity and Feasibility • Future Prospects

3. 3 / 18 Japanese Telescopes in Hawaii Subaru 8.2m Telescope at Mauna Kea, the Big Island MUGNUM 2m Telescope at Haleakala, Maui.

4. 4 / 18 Subaru HDS (High Dispersion Spectrograph) HDS is an echelle spectrograph installed at Subaru Telescope. An iodine cell is available for radial velocity measurements. Instrumental performance: • for V = 8 stars (in 5000 ~ 6000 Å) • R ~ 90000, 3 min exposure  SNR ~ 250 / pixel • for V = 12 stars • R ~ 45000, 15 min exposure  SNR ~ 100 / pixel

5. 5 / 18 Multicolor Active Galactic NUclei Monitoring MAGNUM is a dedicated telescope for AGN research. A wide-field camera has not yet been equipped (future planning). Instrumental performance: • FOV : 1’.5 x 1’.5 square, Band : Optical & IR • differential photometric accuracy • ~ 1.5 mmag (in FOV) • 4 ~ 6 mmag (nodding out of FOV)

6. 6 / 18 Research Projects using these Telescopes Aim: to characterize exoplanets and their systems through transit observations • Ground-based Transmission Spectroscopy • search for atmospheric signatures • previous work : HD 209458 • Measurements of the Rossiter effect • measure the angle between stellar-spin and planetary-orbital axes • ongoing work : TrES-1

7. 7 / 18 Observing Strategies Full transit observation within a single night: • to limit day-to-day instrumental or telluric variations • important for transmission spectroscopy Simultaneous spectroscopy and photometry: • to minimize uncertainty due to orbital ephemeris • important for the Rossiter measurements • transit center accuracy of a few minutes • to monitor transient stellar activities • flare, spots, etc

8. 8 / 18 Transmission Spectroscopy One can in principle detect atmospheric constituents by comparing spectra taken in and out of transit.

9. 9 / 18 -1.47% (base) -1.53% (base) -1.71% (peak) -1.70% (peak) Seager & Sasselov (2000) Brown (2001) Early Theoretical Models Excess 0.1~0.2% absorption was predicted in alkali metal lines with clouds at low pressure (deep cloud decks).

10. 10 / 18 in transit out of transit Charbonneau et al. 2002 HST Results Detection of -0.0232±0.0057 % excess absorption for 12Å band around the sodium doublet: However, it was significantly weaker than the fiducial models (for HD 209458b at least).

11. 11 / 18 1σ 0.06~0.09% for 2Å band 1σ  0.04% for the 12Å band Narita et al. 2005 Previous Work using Subaru HDS We have attempted to search atmospheric signatures: Our sensitivity for HD 209458b was enough to exclude previous fiducial models with a single night observation.

12. 12 / 18 • Requirements to exclude fiducial models with one night • very bright host star : V < 8 • transit duration : longer than 1 hour HD 189733 would be a second target for this study. Motivation of ground-based observations How about other transiting hot Jupiters? We can answer whether the weak sodium absorption is standard or not, or we would be able to detect excess absorption.

13. 13 / 18 Measurements of the Rossiter Effect give us clues to learn about formation mechanism of exoplanets. misalignment parameter λ the degree between the stellar spin axis and the planetary orbital axis in sky projection.

14. 14 / 18 disk-planet interaction (e.g., Type I & II Migration Theory) • core-accretion and radial migration from outside of the snow line • λ would be suppressed. (e.g., Solar System: λ ~ 6 deg) planet-planet interaction (e.g., Jumping-Jupiter model) • if more than 3 giants are formed, the orbits become unstable • this leads to the ejection of one of the giants • the ejected giant can be recaptured neighbor the host star with ~ 30% probability (S. Ida, private communication) • λ would be randomized. Some Models of Hot Jupiter Formation

15. 15 / 18 Past Results All results consistent with zero-misalignment. • HD 209458 (V = 7.65) • -4.4 ± 1.4 deg (Winn et al. 2005) • HD 149026 (V = 8.15) • 11 ± 14 deg (Wolf et al. 2006) • HD 189733 (V = 7.67) • -1.4 ± 1.1 deg (Winn et al. ApJL submitted) All hot Jupiters seem to be formed by standard migration theories.

16. 16 / 18 Ongoing Work We observed TrES-1 (V = 11.8) covering a full transit. MAGNUM photometry (1σ ~ 0.15%) Subaru spectroscopy (SNR ~ 80) We have confirmed transit time by photometry, and obtained 23 radial velocity samples (8~10 m/s accuracy).

17. 17 / 18 • Requirements to determine λ with good accuracy • bright host star : V < 12 • large stellar rotation velocity : > 2 km/s • large transit depth : ~ 1.5 % • long transit duration : ~ 3 hours see e.g., OTS (2005), Gaudi and Winn (2006) for accuracy of λ. Recent new systems (e.g., HAT-P-1) would be future targets. Motivation and Future Work Planetary systems with large λ have not yet discovered. →Migration mechanism is unique standard?

18. 18 / 18 Summary • Our group has initiated transit observation projects: • Ground-based Transmission Spectroscopy • Measurements of the Rossiter effect • Our targets are: • V < 8 (Transmission Spectroscopy) • V < 12 (the Rossiter measurements) • HD189733, HAT-P-1, etc would be good targets • We wish to provide new observational information through our projects.