Further Science of IRD: Synergy with Transiting Planets Norio Narita (NAOJ) Thanks to IRD Transit Group

Members of the IRD Transit Group Norio Narita (Chief: NAOJ) Akihiko Fukui (NAOJ, Okayama Astrophysical Obs.) Teruyuki Hirano (Univ. of Tokyo) Takuya Suenaga (NAOJ, Sokendai) Yasuhiro Takahashi (Univ. of Tokyo) Hiroshi Ohnuki (Tokyo Institute of Technology)

Outline Brief Introduction of Transiting Planets Searching Transiting Planets with IRD Transit Follow-up of RV-detected Planets Transit Survey and RV Follow-up Further Sciences for Transiting Planets Probing Mass-Radius Relation of Small Planets Probing Atmospheres Probing Formation/Migration History Summary

What is Planetary Transits? A phenomenon that a planet passes across in front of its host star Same can happen in exoplanetary systems Venus transit @ Maui, 2012 slightly dimming

What we can learn from transit light curve stellar radius, orbital inclination, mid-transit time ratio of planet/star size planet radius stellar limb-darkening

Combined information provides When combined with RVs RVs provide minimum mass: Mp sin i Transits provide planetary radius: Rp orbital inclination: i Combined information provides planetary mass: Mp planetary density: ρ

Other Merits of Transiting Planets Also, transit observations enable us to infer internal structure of planets atmospheric composition of planets orbital migration history of planets

How to Find Transiting Exoplanets RV survey and transit follow-up HD209458b, HD149026b… GJ436b, GJ3470b Transit survey and RV follow-up HAT, WASP, CoRoT, Kepler GJ1214b, KOI-961b,c,d (=Kepler-42)

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

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

Transit Probabilities for IRD Targets IRD 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

Transit Probabilities for M0V & M6V 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 = 10 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%

Expected Number of Transiting Planets Transit probability for P = 100 days is very low For P = 1-10 days, probability is not bad (1.66-18.5%) 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 several (1-13) transiting planets Importantly, planets with P = 1-10 days can be habitable around M5-6-type dwarfs

Can we follow-up such transiting planets? Answer is YES! IRD targets are typically J < 10 Transiting super-Earths (even Earth size) around M dwarfs cause typically over 1mmag dimming If we can achieve 1mmag sensitivity for J < 10 targets, we can detect such transits We have prepared such high precision transit photometry

Example at Okayama, Japan (J band) ~1mmag is achieved for J~10 target (Fukui et al. in prep.)

Example at IRSF, South Africa (JHKs bands) GJ1214b transit in JHKs bands in 2011 ~1mmag is achieved for J~10 target (Narita et al. submitted) With those telescopes, we plan to follow-up all IRD detected planets.

Transit Survey and RV Follow-up Strategy We have started a collaboration with an UH group (Eric Gaidos, Andrew Mann, et al.) They have prepared a transiting planet candidate catalog based on the WASP archive data and they are preparing a new all-sky nearby M dwarf catalog Based on the transiting planet candidate catalog, we have started transit confirmation observations using 188 cm telescope at Okayama Astrophysical Observatory from 2011

Okayama Proposal Accepted

Ongoing Studies We selected about 50 candidates from the catalog The targets are middel-K – early M dwarfs We aim to follow-up transiting planet candidates via high precision NIR photometry so as to eliminate false positives false positive rate would be as high as ~90% We will follow-up all the candidates before IRD runs We are awarded 23 nights in 2012B semester We expect a few good candidates for RV confirmation with IRD

Summary of Transiting Planet Search If IRD RV survey can find ~70 planets around M dwarfs, we expect to find several transiting planets from transit follow-up From our ongoing transit survey, we expect to find a few transiting planets for IRD RV follow-up Known transiting planets around M dwarfs with J < 10 only 3 (GJ436, GJ1214, GJ3470) IRD + transit observations are quite important to add the number of transiting planets around M dwarfs!

Further Sciences Transiting planets allow us to probe internal structure of planets atmospheric composition of planets orbital migration history of planets

Inferring Internal Structure of Planets Solid line: H/He dominated Dashed line: 100% H2O Dotted line: 75% H2O, 22% Si, 3% Fe core Dot-dashed line: Earth-like (rocky) Charbonneau et al. (2009)

Mass-Radius Relation for “Super-Earths” There is a wide diversity of internal structure of super-Earths. 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

Transit Spectroscopy / Band Photometry star Transit depth depends on wavelength

Case for GJ1214b de Mooij et al. (2011) Green: H2 dominated with solar metallicity Red: H2 dominated with sub-solar metallicity and cloud layer at 0.5 bar Blue: Vapor dominated atmosphere

Our group also works on GJ1214b Up: GJ1214b transit in JHKs bands with IRSF/SIRIUS (NN+ submitted) Left: GJ1214b transit in B band with Subaru/Suprime-Cam (NN+ in prep.)

Inferring Formation History of Planetary Systems scattering captured planets ©Newton Press ejected planet

Recent Understanding of Planet Migration Stellar Spin Planetary　Orbit As for hot Jovian planets, tilted orbits are not so rare. --> Various migration mechanisms indeed occur in the universe.

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.

On Formation History of M Dwarf Planets Are there any tilted or retrograde super-Earths? λ： sky-projected angle between the stellar spin axis and the planetary orbital axis (e.g., Ohta et al. 2005, Gaudi & Winn 2007, Hirano et al. 2010)

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

Conclusion IRD will find transiting planets around M dwarfs The discovered planets will give us further detailed studies on their planetary nature