Testing Planet Migration Theories by Observations of Transiting Exoplanetary Systems 1/39 University of Tokyo Norio Narita

Contents Introduction (15 min) Diversity of Extrasolar Planets Planet Migration Theories Motivation (10 min) Transits and the Rossiter-McLaughlin Effect Recent Results (15 min) Simultaneous Subaru / MAGNUM Observations Analysis and Results Conclusion and Future Prospects (3 min) Significance of Our Results New Targets and Prospects 2/39

Discovery of extrasolar planets 3/39 The first extrasolar planet 51 Peg. b was discovered by radial velocity measurements in More than 200 extrasolae planets have been discovered so far. We can discuss statistics of their distribution.

Diversity of extrasolar planets Semi-major axis – Planet minimum mass Distribution 4/39 Jupiter

Diversity of extrasolar planets (Close-up of the distribution) 5/39 hot Jupiters 1 AU

Semi-major axis – Eccentricity Distribution 6/39 Diversity of extrasolar planets Eccentric Planets Jupiter

How do they form? Giant planets lie at ～ 0.1AU should originally form at larger orbital distances  planetary migration to inner orbits Eccentric planets are common would have mechanisms of eccentricity excitation  How can we explain these features? gravitational interactions with other bodies in protoplanetary disk 7/39

Planet migration theories  disk-planet interaction  “Type I & II migration”  resultant planets would not have large eccentricity  planet-planet interaction  “jumping Jupiter model”  have possibilities to produce large eccentricity  planet-binary companion interaction  “Kozai oscillation” in binary planetary systems  also have possibilities to produce large eccentricity  explain HD system (e=0.927, Wu & Murray 2003) 8/39

Type I & II migration planetary cores form beyond the snow line the cores interact with the surrounding disk planets migrate inward due to torque exchange with the disk Type I migration ： less than ～ 10M E Type II migration ： more than ～ 10M E damping eccentricities and also inclination 9/39 (Leiden Observatory Group) Type I migration Type II migration

Jumping Jupiter model giant planets interact with each other in multi-planet systems leads to orbital instability one planet is thrown into close-in orbit the planet obtains eccentricity and inclination * 10/39 Note *: this inclination is relative to the initial orbital plane

Jumping Jupiter model Marzari & Weidenschilling (2002) inclinationeccentricity periastronsemi-major axis 90% of samples have inclination of more than 10 deg 11/39 produce large eccentricities periastron distance finally become semi-major axis by tidal evolution in hot region

Note: Tidal evolution 12/39 time scale for planetary orbit circularization time scale for stellar spin/planetary orbit coplanarization s: star, p: planet, adopting values for HD b as a typical case P: orbital/rotation period, k: tidal Love number, Q: tidal quality factor (cf. 6×10 4 < Q Jup < 2×10 6 ) Typically τ copl is much longer than τ circ Mardling (2007), Winn et al. (2005)

Kozai mechanism distant binary companion perturbs a planetary orbit leads to “Kozai oscillation” due to conservation of angular momentum the planetary orbit oscillates high/low eccentricity/inclination the planet migrates by tidal evolution 13/39 companion star orbit 1: high eccentricity and inclination orbit 2: low eccentricity and inclination (at least 40 deg) binary orbital plane

Kozai migration 14/39 Wu & Murray (2003) inclination eccentricityperiastron

Differences in outcomes 15/39  disk-planet interaction  negligible eccentricity and inclination  mainstream of migration theories  but cannot explain eccentric planets  planet-planet interaction  possible large eccentricity and inclination  subsequent tidal evolution damps eccentricity  would explain distribution of eccentric planets  planet-binary companion interaction  large eccentricity and inclination

Motivation 16/39 How can we test these theories by observations? eccentricity and inclination are possible clues but eccentricity may be damped within planets’ age inclination (angle between initial and final orbital plane) would be a good diagnostic Stellar spin axis would preserve initial orbital axis * the inclination is equal to the stellar spin axis and the planetary orbital axis (spin-orbit alignment) But can we observe/constraint spin-orbit alignments of exoplanetary systems? Note *: Assumption

Transiting extrasolar planets Charbonneau et al. (2000) Planets pass in front of their host star. periodic dimming in photometry The first transiting planet HD b was reported in /39

What can we learn from transiting planets? Radial Velocity semi-major axis a, minimum mass M p sin i Period P, eccentricity e Transit Photometry orbital inclination * i orb 、 radius ratio R p /R s by combining spectroscopy: radius R p, density ρ Secondary Eclipse thermal emission of planetary surface Transmission Spectroscopy search for atmospheric components Na, H, C, O, H 2 O, SiO detections were reported in HD b (Subaru observations for HD b tomorrow) 18/39 Note *: this inclination is relative to the sky plane

Radial Velocity during Transit hide approaching side → appear to be receding hide receding side → appear to be approaching planet star Transiting planet hides stellar rotation. Radial velocity would have anomalous excursion during transit. 19/39

The Rossiter-McLaughlin effect β Lyrae ： Rossiter 1924, ApJ, 60, 15 Algol: McLaughlin 1924, ApJ, 60, 22 This effect was originally reported in eclipsing binary systems. 20/39

RM effect in transiting exoplanetary system The RM effect was detected in HD b in ELODIE on 193cm telescope Queloz et al. (2000) 21/39

What can we learn from the RM effect? Radial velocity anomaly reflects planet’ trajectory. examples of trajectory time RV anomaly Ohta, Taruya & Suto (2005) 22/39

Definition of λ λ ： sky-projected angle between the stellar spin axis and the planetary orbital axis 23/39

Planetary trajectories and λ Gaudi & Winn (2007) We can measure λ by observations of the RM effect. 24/39

Summary of introduction and motivation  There are several different planet migration theories.  Each theory has different distributions of eccentricity and inclination.  We can observe the RM effect in transiting exoplanetary systems.  We can measure λ(sky-projected spin-orbit alignment) via the RM effect.  λ is an useful diagnostic for testing planet migration theories. A C B D E 25/39

Our recent observations Brief summary Target : TrES-1 (V=11.8) → the faintest target so far Observation : Simultaneous Subaru/MAGNUM observations Challenge : the first RM observation for Subaru & MAGNUM Result : succeeded in detection of the RM effect and placed a constraint on λ Significance 1: extended targets of the RM observations to fainter systems Significance 2: discovery of a possible misaligned system 26/39

Backgrounds of the RM observations 27/39 History of discoveries of target systems before 2005 HD : 2000, V=7.65 TrES-1 : 2004, V=11.8 HD : 2005, V=8.15 HD : 2005, V=7.67 The RM observations were conducted for brighter targets with Keck/HIRES HD : Winn et al HD : Winn et al (HD : Wolf et al. 200?) …

Possible targets of the RM observations Possible targets → Transiting systems brighter than V ～ 12 (for which we can detect the RM effect with Subaru/HDS) Our target : TrES-1, V=11.8 The first challenge for a fainter (V ～ 12) target (also the first RM observation for Subaru/HDS) 28/39

TrES-1 Discovered with 10cm telescope (Alonso et al. 2004) V=11.8 、 K0V 、 V sin I s = 1.08 ± 0.30 km/s ） Poor radial velocity measurements due to its faintness. The star has several spots. ※ Charbonneau et al. (2007) Upper ： TrES-1 Lower ： HD /39

Simultaneous Subaru/MAGNUM observations Radial velocity measurement with Subaru/HDS Photometry with MAGNUM at Haleakala TrES-1 observations with 2 telescopes in Hawaii (UT 2006/6/21) 30/39

RV measurements with Subaru/HDS 20 samples R : Exposure time : 15 min Seeing : ～ 1.0 arcsec S/N : ～ 60 (with iodine cell) Radial velocity analysis by Sato et al. (2002) RV precision : 10 ～ 15 m/s Radial velocities obtained with Subaru/HDS 31/39

Photometry with MAGNUM V band transit light curve obtained with MAGNUM 184 samples Band : V Exposure time : 40 or 60 sec No spot event Photo. precision : 2 mmag Timing precision : ～ 30 sec 32/39

RV model and parameters incorporating published data Keck 12 ( ) RV samples FLWO 1149 (3 transits) photometric samples RM modeling with Ohta, Taruya, & Suto formula(2005) Simultaneous fitting of radial velocity and photometry including the RM effect 15 free parameters K, VsinI s, λ : for radial velocity i orb, u V, u z, R s, R p /R s : for photometry v 1, v 2, v 3 : offsets for radial velocity datasets Tc(234), Tc(235), Tc(236), Tc(238) ： time of transit center 33/39

Note: Constraints on VsinI s External constraint on VsinI s for TrES-1 VsinI s = 1.08 ± 0.30 km/s (Laughlin et al. 2005) Fitting with (a) / without (b) considering the constraint (a) (b) χ 2 minimization with AMOEBA (Numerical Recipes) 34/39

Results of RV fitting a : with, b : without orbital phasetransit phase /39 00

Constraints on VsinI s and λ Contours : ⊿ χ 2 =1,00, ⊿ χ 2 =2.30, ⊿ χ 2 =4.00, ⊿ χ 2 = /39 (a) ： VsinI s = 1.3 ± 0.3 [km/s], λ= 30 ± 21 [deg] (b) ： VsinI s = 2.5 ± 0.8 [km/s], λ= 48 ± 17 [deg]

Summary of Our Recent Results We detected the RM effect in TrES-1 (V ～ 12) TrES-1 is the faintest target so far We confirm that similar observations are possible for other faint systems We put a constraint on λ in TrES-1 for the first time large uncertainty, but at least we confirmed that the planet orbits in a prograde manner possible misaligned (over 10 deg) system additional RM observations would pin down λ the first candidate of the jumping Jupiter model 37/39

What’s next? New targets were discovered in 2006 & ground-based transit survey teams (XO, TrES, HAT, WASP) succeeded in detecting new transiting systems all transit survey teams target V less than ～ 12 also ESA’s satellite mission (CoRoT) started in : XO-1, TrES-2, HAT-P-1, WASP-1, WASP : CoRoT-1, TrES-3, XO-2, XO-3, HAT-P-2, GJ 436 (recent news) : XO-4, TrES-4, HAT-P-3, HAT-P-4, more to come! observational / statistical studies have become possible 38/39

Future Prospects We can measure the RM effect of new transiting systems By measuring the distribution of spin-orbit alignment, we can test planet migration theories already we have possible misaligned target TrES-1 → further constraint on λ at least 15 new targets We can present observational / statistical distribution of spin- orbit alignment within several years 39/39