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

2. 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)

3. 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

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

5. 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

6. 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

7. 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

8. 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)

9. 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?

10. 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

11. 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 = days : f=0.35 (+0.45, -0.11)
If IRD monitor ~200 M dwarfs, IRD can find ~70 super-Earths

12. Transit Probabilities for M0V & M6V
Rs ～ 0.62 Rsun ～ AU
P = 100 days -> a ～ AU, Transit Probability： Rs/a ～ 0.86%
P = 10 days -> a ～ AU, Transit Probability： Rs/a ～ 4%
P = 1 days -> a ～ AU, Transit Probability： Rs/a ～ 18.5%
M6V
Rs ～ 0.1 Rsun ～ AU
P = 10 days -> a ～ AU, Transit Probability： Rs/a ～ 0.24%
P = 10 days -> a ～ AU, Transit Probability： Rs/a ～ 1.66%
P = 1 days -> a ～ AU, Transit Probability： Rs/a ～ 7.75%

13. Expected Number of Transiting Planets
Transit probability for P = 100 days is very low
For P = 1-10 days, probability is not bad ( %)
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

14. 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

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

16. 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.

17. 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

18. Okayama Proposal Accepted

19. 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

20. 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!

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

22. 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)

23. 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

24. Transit Spectroscopy / Band Photometry
star
Transit depth depends on wavelength

25. 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

26. 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.)

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

28. 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.

29. 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.

30. 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)

31. 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

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