June. 4, 2015 @ NAOJ Probing the Dynamical History of Exoplanets: Spectroscopic Observaons of Transing Systems

Teruyuki Hirano ©NASA Outline

1. Dynamical History of Close-in Planets 2. Measurements of the Stellar Obliquity 3. Observaon of the Rossiter-McLaughlin (RM) Effect 4. Interpretaon of the Past RM Result 5. Towards Smaller Planets 6. Summary Distribuon of Exoplanets I

100

10 B ] J [M 1 A

0.1 anet mass l p Snow Line 0.01 C

0.001 0.001 0.01 0.1 1 10 100 semi-major axis [AU] Distribuon of Exoplanets II

1

0.1 orbital eccentricity

0.01 0.01 0.1 1 10 100 semi-major axis [AU] Formaon of Close-in Giant Planets

The Standard Scenario

→ Close-in giants have originally formed at a few AU away from their host stars, then migrated inward by some migraon processes.

ØWhat process can make planets migrate? ØIs there any possibility to observaonally disnguish among migraon scenarios ?

5 Migraon Processes

1. Interacons between proto-planets and proto-plantary disk → Planets had gradually migrated inward due to gravitaonal interacons with proto-planetary disk (e.g. Lin et al. 1996, Lubow & Ida 2010)

2. Planet-planet scaering (or Kozai cycles) + dal interacons → When mulple planets form or there exists a companion star, they interact with each other and somemes cause orbital crossing, which can pump up eccentricies. Subsequent dal interacons with host stars may cause orbital circularizaon. (e.g. Chaerjee et al. 2008, Wu et al. 2007, Fabrycky & Tremaine 2007)

6 © Weidenschilling and Marzari 1996 Migraon Processes

1. Interacons between proto-planets and proto-plantary disk → Planets had gradually migrated inward due to gravitaonal interacons with proto-planetary disk (e.g. Lin et al. 1996, Lubow & Ida 2010) → small e and stellar obliquity

2. Planet-planet scaering (or Kozai cycles) + dal interacons → When mulple planets form or there exists a companion star, they interact with each other and somemes cause orbital crossing, which can pump up eccentricies. Subsequent dal interacons with host stars may cause orbital circularizaon. (e.g. Chaerjee et al. 2008, Wu et al. 2007, Fabrycky & Tremaine 2007) → large e and stellar obliquity

7 © Weidenschilling and Marzari 1996 Measurements of the Stellar Obliquity Measurement of the stellar obliquity is a unique method to probe the dynamical history of exoplanets! a. The Rossiter-McLaughlin effect -> High dispersion spectroscopy during planetary transits (e.g., Queloz 2002, Winn et al. 2005) b. Spot-crossing Method -> Modeling of anomaly in transit light-curves (e.g., Sanchis-Ojeda, et al. 2011) c. VsinI Method -> Spectroscopic determinaon of the rotaon velocity + photometric determinaon of the rotaon period (e.g., Hirano et al. 2012) d. Asteroseismology -> High cadence photometry of pulsang stars (e.g., Chaplin et al. 2013) e. Gravity-darkening Method -> Modeling of asymmetry in transit light- curves → Kamiaka’s talk The Rossiter-McLaughlin (RM) Effect λ = 0° λ = 50°

approaching receding

planet’s orbit

during transit ←vercal axis: radial veliocity anomaly during a transit RV anomaly RV anomaly

time [h] time [h]

Through the RM effect, we can esmate the angle between the stellar spin axis and the planetary orbital axis, which is closely related to the planetary migraon. 9 Results by Subaru/HDS

Subaru RV 40

20 ] -1 0 v [m s !

-20

Subaru (this work) -40 Keck (P08)

30 ]

-1 20 10 0 -10 -20 Residual [m s -30 -0.04 -0.02 0 0.02 0.04 Orbital Phase ↑ HAT-P-16: ↑ HAT-P-7: Teff = 6158 ± 80 K Teff = 6350 ± 80 K λ = -8.4° ± 7.0° λ = -132.6° +10.5° -16.3° VsinIs = 3.9 ± 0.3 km/s VsinIs = 2.3 ± 0.6 km/s T.H. + in prep. Narita et al. 2009 RM Measurement for a Mulple Transing System

Name of Candidate Orbital Period Planet Radius Kepler-89b 3.7 days 0.13 RJ Kepler-89c 10.4 days 0.31 RJ

Kepler-89d 22.3 days 0.83 RJ Kepler-89e 54.3 days 0.49 RJ

40

20 Kepler-89 (KOI-94): ] -1 0 v [m s ∆ Teff = 6116 ± 30 K -20 λ = -6° -11° +13° VsinIs = 8.01 ± 0.73 km/s -40 Kepler-89d

30 T.H.+ 2012b, ApJ Letters ]

-1 20 10 0 -10 This result was later confirmed -20 Residual [m s -30 by Albrecht et al. (2013) -0.01 -0.005 0 0.005 0.01 Orbital Phase Mulple transing systems are generally aligned!

15 2.0•105 ← RM1.5•105 measurements for Kepler-25 10 1.0•105

(multi-planet5.0•104 system):

5 0 −20 0 20 ) − 1 0 Teff = 6190 ± 80 K 12 12 −5 λ = 7°±8° RV (m s −10 VsinIs = 8.7 ± 1.3 km/s )

10 − 1 10 −15

0.23 0.26 10 Obliquity measurements for other multi-

8 ) 8

− 1 5 planetv sin i (km s systems generally show good spin- 0 orbit alignment (Sanchis-Ojeda et al. 2012, −5 6 6 −10 Huber et al. 2013). O − C (m s −15

0 2.0•104 4.0•104 6.0•104 8.0•104 1.0•105 1.2•105 1.4•105

−6 −4 −2 0 2 The only− exception20 0 is 20Kepler-56 (multiple, Time (hr) but misaligned;λ (deg)Huber et al. 2013). Albrecht et al. 2013, ApJ

A companion is present outside of the planetary system, which might be responsible for the misalignment in Kepler-56. Summary of RM Measurements

180

150 WASP-8 b 120 HAT-P-11 b |λ| 90 60 HD 80606 b proj. obliquity [deg] 30 HD 17156 b 0

5000 6000 7000 8000

80 ] -1 60 [km s

star 40

v sin i 20

5000 6000 7000 8000 Teff [K]

Albrecht et al. 2012 Correlaon between Stellar Obliquity and Relave Tidal Timescale Albrecht et al. 2012

180 |λ| HAT−P−7 b 150 WASP−8 b 120 WASP−33 b HAT−P−11 b 90 HAT−P−32 b

WASP−12 b 60 HD 80606 b XO−3 b

proj. obliquity [deg] 30 KOI−13 b

HD 17156 b 0

100 102 104 106 108 relative tidal−dissipation timescales τCE τRA [yr] ↑ relative tidal damping timescale of stellar obliquity (based on Zahn 1977)

Assuming that planet-planet scatterings are the dominant channel for the formation of HJ

subsequent tidal interactions “realign” the stellar spin and the planet orbital axes. Quiescent v.s. Chaoc migraons

• Quiescent migraons (i.e., disk-planet interacons): ü The presence of close-in planets in mean moon resonance ü Mulple transing systems are generally aligned. ü Misaligned systems are formed by stellar internal gravity waves independently of the planets? (Rogers et al. 2012)

• Chaoc migraons: ü The correlaon between the stellar obliquity and relave dal damping mescale ü Existence of highly eccentric hot Jupiters (e.g., HD 80606b) To Sele This Issue… Previous Targets of RM Measurements host star Single Transing System Mulple Transing System cool (Teff < 6250 K) many a few hot (Teff > 6250 K) many No observaon

180

ü One solution to partly settle the 150 WASP-8 b debate is to observe the RM 120 HAT-P-11 b effect for “hot multiple” systems. 90 60 HD 80606 b ü So far, no hot multiple systems proj. obliquity [deg] 30 HD 17156 b 0 have been investigated for 5000 6000 7000 8000 80

obliquity measurements. ] -1 60 [km s ü There are a few hot multiple star 40

systems detected by Kepler (e.g., v sin i 20 KOI-89). 5000 6000 7000 8000 T [K] Worth a try! eff Towards Smaller Planets Limitaon of the RM Measurements a. The RM measurements have been conducted for systems with hot Jupiters (Neptunes). b. When the size of the transing planet becomes small (~ Earth- sized planet), the detecon of the RM effect becomes very challenging.

→ ΔvRM 〜 - f ・ V sin Is・√(1-b^2) c. In order to confirm or refute possible hypothesis on the planetary migraon (and relevant dal interacon), we need to expand the parameter space for which the spin-orbit angle is invesgated. Esmate of Stellar Rotaon Periods

KOI 988 1.015 ü Some of the light-curves 1.010 1.005 taken by Kepler spacecra 1.000 0.995

show periodic flux variaons Relative flux 0.990 due to rotaon of starspots. 0.985 210 220 230 240 BJD−2454900 [days] 2.0•104 ü From such light-curves, we 1.5•104 1.0•104 can esmate the rotaonal ower P periods of planet hosng 5.0•103 0 stars. 0 5 10 15 20 Period of rotation [days] Esmaon of Stellar Inclinaons by Starspots 1

2

534/%-).&#+-43)46+$ $-%334&)$5+/)46+$ λ

I$ 7 !"#$%&'%&($)*+&%,-+./0 I.

ü The rotational period Ps of the host star is estimated by Kepler photometry. ü The projected rotational velocity (V sin Is) and stellar radius are estimated by spectroscopy.

We can estimate stellar inclination Is. a. Since the orbital inclinaon of a transing exoplanet is close to 90°, a small value of Is implies a spin-orbit misalignment.

b. This method can be applied regardless of the size of the planet, enabling us to discuss spin-orbit alignment/misalignment for smaller exoplanets. Results 1

We observed about 10 KOI systems and estimated VsinIs along with stellar radii.

20 x axis -> rotational velocities o Is=90 estimated by Kepler multiple photometry 15 269 262 ] -1 y axis -> projected rotational o 974 Is=45 velocities estimated [km s 10 s by spectroscopy 257 o

V sin I Is=30 5 280 Solid line indicates 367 261 Veq = V sin Is, 0 0 5 10 15 20 suggesting spin-orbit -1 Veq [km s ] alignments. T.H.+ 2012, ApJ, 756, 66 KOI-261 may have a possible spin-orbit misalignment along the line-of-sight. Results 2 We observed additional 25 systems.

20 o 10 I =90 (a) single (b) multi s o Is=90

15 ] 8 ] -1 1 - I =45o 6 s [km s

[km s o

10 I =45 s s s 4 o 2002 Is=30

1890 V sin I V sin I o 2261 323 Is=30 5 988 2026 2 285 304

0 0 0 5 10 15 20 0 2 4 6 8 10 -1 -1 Veq [km s ] Veq [km s ] T.H.+ 2014, ApJ

ü All the systems here have only Earth- or Neptune-sized planets. ü Some multiple systems show possible spin-orbit misalignment. Posterior distribuons of I s

2.5 blue single red multi 2 black isotropic

1.5

1 Probability Density 0.5

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4

Is [radian]

ü We computed the posterior distribution of Is for each system. ü The solid lines indicate the averaged posteriors for single and multiple systems. ü The two distributions (red and blue) seem slightly different from each other. Summary

1. Measurements of the stellar obliquity have revealed a diversity in the spin-orbit relaon, and yielded new hypotheses on the dynamical origin of exoplanets.

2. Observaonal results of the RM measurement imply that some close- in giant planets have experienced quiescent migraon (e.g., Kepler-89), while others are produced by more chaoc processes. The reason for this discrepancy between the two dynamical origins is not known.

3. Measurement of the stellar inclinaon is a unique technique to discuss spin-orbit relaons for systems with smaller planets. Previous observaon showed that transing systems with small planets generally have good spin-orbit alignment. The distribuons of stellar inclinaons for single and mulple systems show a slight difference (Morton & Winn 2014).