Norio Narita (NAOJ) On behalf of IRD Transit Group

1. Transiting Exoplanet Search and Characterization with Subaru's New Infrared Doppler Instrument (IRD) Norio Narita (NAOJ) On behalf of IRD Transit Group

2. Outline of This Talk • Searching new transiting planets around cool host stars before and after IRD’s first light • Characterizing new transiting planets with IRD and other telescopes / instruments

3. How to Find Transiting Exoplanets • RV detection and transit follow-up • HD209458b, HD189733b, HD149026b… • GJ436b, GJ3470b… • How many transiting planets can be discovered with IRD? • Transit survey and RV follow-up • TrES, HAT, WASP, XO, CoRoT, Kepler, MEarth… • GJ1214b, Kepler planets

4. The First Discovery of a Transiting Planet RVs can predict possible transit times Charbonneau et al. (2000) Transits of HD209458b Mazehet al. (2000) RVs of HD209458b How often does it happen?

5. Some Characteristics of Transiting Planets planetary radius : stellar radius： semi-major axis： Toward Earth orbital period： Transit Probability： Transit Depth： Transit Duration： ～ Rs/a ～ (Rp/Rs)2 ～ RsP/a π

6. Transit Probabilities for IRD Targets • IRD’s main targets are M dwarfs • Bonfils et al. (2011) reported results of HARPS RV survey for M dwarfs that super-Earths are frequent • P = 1-10days : f=0.36 (+0.25, -0.10) • P = 10-100days : f=0.35 (+0.45, -0.11) • If IRD monitor ~200 M dwarfs, IRD can find ~70 super-Earths

7. Transit Probabilities forM0V & M6V • M0V • Rs～0.62 Rsun～ 0.00288 AU • P = 100 days -> a ～0.334 AU, Transit Probability： Rs/a ～ 0.86% • P = 10 days -> a ～ 0.072 AU, Transit Probability： Rs/a ～ 4% • P = 1 days -> a ～0.0155 AU, Transit Probability： Rs/a ～ 18.5% • M6V • Rs～ 0.1 Rsun～ 0.000465 AU • P = 100 days -> a ～0.195 AU, Transit Probability： Rs/a ～ 0.24% • P = 10 days -> a ～0.042 AU, Transit Probability： Rs/a ～ 1.66% • P = 1 days -> a ～0.009 AU, Transit Probability： Rs/a ～ 7.75%

8. Expected Number of IRD Transiting Planets • Transit probability for P = 100 days is too low • For P = 1-10 days, probability is not bad (several %) • IRD aims detections of ~70 planets by RV method • If 70 super-Earths at P = 1-10 days are discovered around M dwarfs, there would be a few new transiting planets • Planets with P = 1-10 days can be habitable around M5-6-type dwarfs

9. Ongoing/Future Transit Surveys around M Dwarfs • Transit surveys before IRD’s first light • MEarth (Harvard) and other teams in the world • SEAWOLF survey (UH/NAOJ/etc) • MOA-II transit survey (NAOJ/MOA) • Future Space-based Survey with IRD follow-up • TESS from 2017 (MIT/NASA)

10. SEAWOLF Survey • Transit survey using Super-WASP archive data and Lepine & Gaidos M dwarf catalog • High precision transit follow-up by northern hemisphere telescopes • IRD transit group used Okayama 1.88m telescope in Japan • Unfortunately no detection, but constrain the occurrence rate of hot Neptunes around late-K & M stars as 5.3 ± 4.4 % (Gaidos+ 2013) target distribution occurrence rate

11. Transit Survey for nearby M dwarfs by 1.8m MOA-II • Nearby (J<11) M dwarfs are sparsely distributed in the sky (~1/deg2) • High photometric precision (~1mmag) is required to detect super-Earths/Neptunes Wide FOV, 2m class telescope is ideal The MOA-II telescope in New Zealand the MOA-II telescope • 1.8m mirror • 10 x CCD (2k x 4k) • 2.2 deg2 FOV • Dedicated for planetary microlensing survey during winter (Mar. – Oct.) Started transit survey during summer season from 2013 Nov (PI: A. Fukui). prime-focus camera

12. Transit Survey for nearby M dwarfs by 1.8m MOA-II Field selection/observations The selected fields • Selected 6 fields among -20° < Dec. < -5° ; each contains ~10 bright (J < 11) M dwarfs • One field is taken 10 times in a row with a cadence of 80 sec Galactic plane Expected yields • Can detect planets showing > 0.2 % transit depth from several years survey • Kepler detected 22 candidates showing >0.2% transit depth among 3600 M dwarfs • ~0.4 planets/several years can be detected among our targets (total 65 M dwarfs) -> similar to MEarth survey • monitoring stellar activity for IRD targets Example of defocused target images

13. All-Sky Transit Survey: TESS Led by MIT/NASA and will be launched in 2017 2 IRD science members are participating in TESS Science Working Group

14. TESS and IRD • Targets • Bright nearby stars with I = 4-13 mag (FGKM stars) • Period of detectable planets • typically less than 10 days (26-day monitoring for 1 field) • up to ~60 days for JWST optimized fields • Planetary orbits with less than 10 (60) days period lie in habitable zone around mid (early) M stars • expected to discover ~500 Earths /super-Earths and Subaru IRD will contribute for RV follow-up of M dwarfs

15. Outline of This Talk • Searching new transiting planets around cool host stars before and after IRD’s first light • Characterizing new transiting planets with IRD and other telescopes / instruments

16. What can we learn from transits and RVs • RVs provide • minimum mass: Mp sin I • eccentricity: e • Transits provide • planetary radius: Rp • orbital inclination: i • Combined information provides • planetary mass: Mp • planetary density: ρ

17. Mass-Radius Relation for “Super-Earths” Future transit surveys and IRD can fill this figure out. Theoretical models can predict mass-radius relation for a variety of bulk compositions, but models are often degenerated. How can we discriminate compositions? Courtesy of M. Ikoma

18. Transmission Spectroscopy star Transit depths depend on wavelength reflecting atmospheres

19. Differences of Super-Earths’ Transmission Spectra Courtesy of Yui Kawashima Super-Earths’ atmospheric compositions are also important to learn origins of them -> cf. M. Ikoma’s talk

20. Testing Planet Migration Theories • Transiting planets are useful to test planet migration theories by orbital eccentricity and obliquity • Population synthesis for small planets around M dwarfs can predict distributions of such parameters • IRD can measure both orbital eccentricity and obliquity by RV observations • obliquity by the Rossiter-McLaughlin effect • We can provide new information to theorists

21. The Rossiter-McLaughlin effect When a transiting planet hides stellar rotation, star planet planet the planet hides the approaching side → the star appears to be receding the planet hides the receding side → the star appears to be approaching radial velocity of the host star would have an apparent anomaly during transits.

22. Observable Orbital Obliquity Are there any tilted or retrograde super-Earths? λ： sky-projected angle between the stellar spin axis and the planetary orbital axis (e.g., Ohtaet al. 2005, Gaudi & Winn 2007, Hirano et al. 2010)

23. Merit of IRD for the RM study • M dwarfs are very faint in visible wavelength • Measurements of the RM effect need enough time-resolution and RV-precision • Actually, GJ436 (V=10.6, J=6.9), GJ1214 (V=14.7, J=9.8), GJ3470 (V=12.3, J=8.8) are quite difficult targets with the current visible instruments • IRD can significantly improve time-resolution and enable us to determine λ for those planets • We can test predictions of planet population synthesis

24. Conclusion • IRD transit group is working on transit-related science cases for Subaru IRD • Subaru IRD will be useful for both searching and characterizing new transiting super-Earths