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

IRD Science Groups RV group (chief: Bun’ei Sato) – Talk by Takayuki Kotani and Poster by Masashi Omiya Transit group (chief: Norio Narita) – with Akihiko Fukui and Teruyuki Hirano – preparing IRD’s transit-related science cases M dwarf group (chief: Wako Aoki) Theory group (chief: Eiichiro Kokubo)

Outline of This Talk 1.Searching new transiting planets around cool host stars before and after IRD’s first light 2.Characterizing new transiting planets with IRD and other telescopes / instruments

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

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

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

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

Transit Probabilities for M0V & M6V M0V – 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 = 100 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%

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

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)

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

Transit Survey for nearby M dwarfs by 1.8m MOA-II Nearby (J<11) M dwarfs are sparsely distributed in the sky (~1/deg 2 ) 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 1.8m mirror 10 x CCD (2k x 4k) 2.2 deg 2 FOV Dedicated for planetary microlensing survey during winter (Mar. – Oct.) Started transit survey during summer season from 2013 Nov (PI: A. Fukui). the MOA-II telescope prime-focus camera

Transit Survey for nearby M dwarfs by 1.8m MOA-II 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 The selected fields 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 Galactic plane Example of defocused target images Field selection/observations

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

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

Outline of This Talk 1.Searching new transiting planets around cool host stars before and after IRD’s first light 2.Characterizing new transiting planets with IRD and other telescopes / instruments

What can we learn from transits and RVs RVs provide  minimum mass: M p sin I  eccentricity: e Transits provide planetary radius: R p orbital inclination: i Combined information provides  planetary mass: M p  planetary density: ρ

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

Transmission Spectroscopy star Transit depths depend on wavelength reflecting atmospheres

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

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

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

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., 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 We can test predictions of planet population synthesis

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