June. 4, 2015 @ NAOJ Probing the Dynamical History of Exoplanets: Spectroscopic Observaons of Transi<ng 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 Distribu<on 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] Distribu<on 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 dis<nguish among migraon scenarios ? 5 Migraon Processes 1. Interac<ons between proto-planets and proto-plantary disk → Planets had gradually migrated inward due to gravitaonal interac<ons with proto-planetary disk (e.g. Lin et al. 1996, Lubow & Ida 2010) 2. Planet-planet scaering (or Kozai cycles) + <dal interac<ons → When mul<ple planets form or there exists a companion star, they interact with each other and some<mes cause orbital crossing, which can pump up eccentrici<es. Subsequent <dal interac<ons 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. Interac<ons between proto-planets and proto-plantary disk → Planets had gradually migrated inward due to gravitaonal interac<ons 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 interac<ons → When mul<ple planets form or there exists a companion star, they interact with each other and some<mes cause orbital crossing, which can pump up eccentrici<es. Subsequent <dal interac<ons 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 ←ver<cal axis: radial veliocity anomaly during a transit RV anomaly RV anomaly time [h] time [h] Through the RM effect, we can es<mate 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 Mul<ple Transi<ng 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 Mul<ple transi<ng 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 ) 1 10 − 10 −15 0.23 0.26 10 Obliquity measurements for other multi- 8 ) 1 8 − 5 planetv sin i (km s systems generally show good spin- 0 orbit alignment (Sanchis-Ojeda et al. 2012, −5 C (m s 6 − 6 −10 Huber et al. 2013). O −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. Chao<c migraons • Quiescent migraons (i.e., disk-planet interac<ons): ü The presence of close-in planets in mean mo<on resonance ü Mul<ple transi<ng systems are generally aligned. ü Misaligned systems are formed by stellar internal gravity waves independently of the planets? (Rogers et al. 2012) • Chao<c 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 Se^le This Issue… Previous Targets of RM Measurements host star Single Transing System Mul<ple Transi<ng 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 transi<ng planet becomes small (~ Earth- sized planet), the detec<on 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 interac<on), we need to expand the parameter space for which the spin-orbit angle is inves<gated. Es<mate 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 es<mate the rotaonal ower P periods of planet hos<ng 5.0•103 0 stars. 0 5 10 15 20 Period of rotation [days] Es<maon 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 transi<ng 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.