Subaru Measurements of the Rossiter-McLaughlin Effect andDirect Imaging Observations for Transiting Planetary Systems

Norio NaritaNational Astronomical Observatory of Japan

Outline

• Introduction of orbits of Solar system bodies and

exoplanets

• Planet migration models

• Rossiter-McLaughlin effect and Subaru results

• Direct imaging of spin-orbit misaligned systems

• Summary and future strategy

Orbits of the Solar System Planets

All planets orbit in the same direction

small orbital eccentricities

At a maximum (Mercury) e = 0.2

small orbital inclinations

The spin axis of the Sun and the orbital axes of

planets are aligned within 7 degrees

In almost the same orbital plane (ecliptic plane)

The configuration is explained by core-accretion models

in a proto-planetary disk

Orbits of Solar System Asteroids and SatellitesAsteroids

most of asteroids orbits in the ecliptic plane significant portion of asteroids have tilted orbits 24 retrograde asteroids have been discovered so far

Satellites orbital axes of satellites are mostly aligned with the

spin axis of host planets dozens of satellites have tilted orbits or even

retrograde orbits (e.g., Triton around Neptune)These highly tilted or retrograde orbits are explained by

gravitational interaction with planets or Kozai mechanism

Motivation

Orbits of the Solar System bodies reflect

the formation history of the Solar System

How about extrasolar planets?

Planetary orbits would provide us information

about formation histories of exoplanetary systems!

Semi-Major Axis Distribution of Exoplanets

Need planetary migration mechanisms!

Snow line

Jupiter

Standard Migration Models

consider gravitational interaction between

proto-planetary disk and planets

• Type I: less than 10 Earth mass proto-planets

• Type II: more massive case (Jovian planets)

well explain the semi-major axis distribution

e.g., a series of Ida & Lin papers

predict small eccentricities and small inclination for

migrated planets

Type I and II migration mechanisms

Eccentricity Distribution

Cannot be explained by Type I & II migration model

Jupiter

Eccentric Planets

Migration Models for Eccentric Planets

consider gravitational interaction between

planet-planet (planet-planet scattering models)

planet-binary companion (Kozai migration)

may be able to explain eccentricity distribution

e.g., Nagasawa+ 2008, Chatterjee+ 2008

predict a variety of eccentricities and also misalignments

between stellar-spin and planetary-orbital axes

ejected planet

Example of Misalignment Prediction

0 30 60 90 120 150 180 deg

Nagasawa, Ida, & Bessho (2008)

Misaligned and even retrograde planets are predicted.

How can we test these models by observations?

Planetary transits

2006/11/9transit of Mercury

observed with Hinode

transit in the Solar System

If a planetary orbit passes in front of its host star by chance,we can observe exoplanetary transits as periodical dimming.

transit in exoplanetary systems(we cannot spatially resolve)

slightly dimming

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 planetstar

When a transiting planet hides stellar rotation,

radial velocity of the host star would havean apparent anomaly during transits.

What can we learn from RM effect?

Gaudi & Winn (2007)

The shape of RM effectdepends on the trajectory of the transiting planet.

well aligned misaligned

Radial velocity during transits = the Keplerian motion and the RM effect

Observable parameter

λ ： sky-projected angle betweenthe stellar spin axis and the planetary orbital axis(e.g., Ohta+ 2005, Gaudi & Winn 2007, Hirano et al. 2010)

1. HD209458 Queloz+ 2000, Winn+ 20052. HD189733 Winn+ 20063. TrES-1 Narita+ 20074. HAT-P-2 Winn+ 2007, Loeillet+ 20085. HD149026 Wolf+ 20076. HD17156 Narita+ 2008,2009, Cochran+ 2008, Barbieri+ 20097. TrES-2 Winn+ 20088. CoRoT-2 Bouchy+ 20089. XO-3 Hebrard+ 2008, Winn+ 2009, Narita+ in prep.10. HAT-P-1 Johnson+ 200811. HD80606 Moutou+ 2009, Pont+ 2009, Winn+ 200912. WASP-14 Joshi+ 2008, Johnson+ 200913. HAT-P-7 Narita+ 2009, Winn+ 200914. CoRoT-3 Triaud+ 200915. WASP-17 Anderson+ 200916. CoRoT-1 Pont+ 200917. WASP-3 Simpson+ 2010, Tri?+ 201018. Kepler-8 Jenkins+ 201019. TrES-4 Narita+ 201020. HAT-P-13 Winn+ 2010, Hirano+ in prep. and more and

more

Previous studiesRed: EccentricBlue: BinaryGreen: Both

Subaru Radial Velocity Observations

Iodine cell

HDS

Subaru

Prograde Planet: TrES-1bOur first observation with Subaru/HDS

We confirmed a prograde orbit and

the spin-orbit alignment of the planet.

NN et al. (2007)

Ecctentric Planet: HD17156b

Well aligned in spite of its eccentricity.

Eccentric planet with the orbital period of 21.2 days.

NN et al. (2009a)λ = 10.0 ± 5.1 deg

Possibly Binary System Planet: TrES-4b

NN et al. in prep.

Well aligned in spite of its binarity.

NN et al. 2010a. λ = 6.3 ± 4.7 deg

Retrograde Exoplanet: HAT-P-7b

NN et al. (2009b)

Winn et al. (2009)

More Retrograde Exoplanets

WASP-17bTriaud et al. submitted

WASP-15b

Queloz et al. (2010)WASP-8b

Cameron et al. (2010)

WASP-33b

Summary of previous RM Studies

4/7: misaligned/eccentric but not binary

• 1/4: retrograde/misaligned (eccentric but not binary)

0/3: misaligned/binary but not eccnetric

2/2: misaligned/eccentric and binary

1/2: retrograde/misaligned (eccentric and binary)

6/15: misaligned/not eccentric nor binary

• 4/6: retrograde/misaligned (not eccentric nor binary)

12/27: misaligned/all, 6/12: retrograde/misaligned

• biased, since aligned planets are less interesting and unpublished

Recent speculation for RM results

significant portion of exoplanets seem to have migrated through

p-p scattering or Kozai process

ratio of Type I & II migration may be less than previously thought

(Winn et al. 2010)

one cannot distinguish between p-p scattering and Kozai

migration by spin-orbit misalignments or eccentricities alone

Need to search for counterparts of migration processes

very long term radial velocity measurements

direct imaging

MotivationSpin-orbit misaligned or eccentric planets should have outer

massive bodies to explain their orbits

detection of such bodies are very useful to discriminate planet

migration processes of planetary systems

if a binary companion exists

we can constrain its initial configuration of the system based on the

Kozai migration, or the system formed through p-p scattering

even if no binary companion exist

such a system formed through p-p scattering

useful to discriminate planet migration mechanisms

SEEDS ProjectSEEDS: Strategic Exploration of Exoplanets and Disks with Subaru

First “Subaru Strategic Observations” PI: Motohide Tamura

Using Subaru’s new instrument: HiCIAO

total 120 nights in 5 years (10 semesters) with Subaru 500+ targets Direct imaging and census of giant planets and brown dwarfs around

solar-type stars in the outer regions (a few - 40 AU) Exploring proto-planetary disks and debris disks for origin of their

diversity and evolution at the same radial regions

Subaru’s new instrument: HiCIAO• HiCIAO: High Contrast Instrument for next

generation Adaptive Optics• PI: Motohide Tamura (NAOJ)

– Co-PI: Klaus Hodapp (UH), Ryuji Suzuki (TMT)• Curvature-sensing AO with 188 elements and

will be upgraded to SCExAO 1024 elements• Commissioned in 2009• Specifications and Performance

– 2048x2048 HgCdTe and ASIC readout– Observing modes: DI, PDI (polarimetric mode),

SDI (spectral differential mode), & ADI; w/wo occulting masks (>0.1")

– Field of View: 20"x20" (DI), 20"x10" (PDI), 5"x5" (SDI)

– Contrast: 10^-5.5 at 1", 10^-4 at 0.15" (DI)– Filters: Y, J, H, K, CH4, [FeII], H2, ND– Lyot stop: continuous rotation for spider block

First Target: HAT-P-7

not eccentric, but misaligned (NN+ 2009b, Winn et al. 2009)

long-term RV trend (Winn et al. 2009, &unpublished Subaru data)

HJD - 2454000

Winn et al. (2009) 2008 and 2010 Subaru data2007 and 2009 Keck data

very interesting target for direct imaging observation!

Observation and AnalysisSubaru/HiCIAO Observation: 2009 August 6

Setup: H band, DI mode (FoV: 20’’ x 20’’)

Total exposure time: 9.75 min

Angular Differential Imaging (ADI: Marois+ 06) technique with

Locally Optimized Combination of Images (LOCI: Lafreniere+ 07)

Calar Alto / AstraLux Norte Observation: 2009 October 30

Setup: I’ and z’ bands, FoV: 12’’ x 12’’

Total exposure time: 30 sec

Lucky Imaging technique (Daemgen+ 09)

Result Images

Left: Subaru HiCIAO image, 12’’ x 12’’, Upper Right: HiCIAO LOCI image, 6’’ x 6’’Lower Right: AstraLux image, 12’’ x 12’’

N

E

Characterization of binary candidates

Based on stellar SED (Table 3) in Kraus and Hillenbrand (2007).Assuming that the candidates are main sequence stars

at the same distance as HAT-P-7.

projected separation: ~1000 AU

Constraints on outer bodies

Contrast: 7x10-4@0.3'’(100AU), 2x10-4@0.5'’(160AU), 6x10-5@1.0'’(320AU)

Corresponding 5σ detectable mass: 110 MJ, 80 MJ, 70 MJ

massive planets and brown dwarfs were not excluded at this point

H band contrast ratio 5σ detectable mass

Initial configuration for the Kozai migration

If either of the candidates is a real binary companion

By the angular momentum conservation (Kozai mechanism)

• , : : semi-major axis and eccentricity of planet

• : mutual inclination between orbital planes of planet and binary

• 0: initial condition, n: now

necessary condition to initiate tidal evolution:

within 82.5 – 97.5 deg (even for the most optimistic case)

Allowed region for additional bodies

The kozai migration cannot occur if the timescale of orbital precession due to an additional body PG,c is shorter than that caused by Kozai mechanism PK,B (Innanen et al. 1997)

Kozai migration allowed

Kozai migration forbidden

boundary

Possible additional planet ‘HAT-P-7c’

HJD - 2454000

Winn et al. (2009c) 2008 and 2010 Subaru data2007 and 2009 Keck data

Kozai migration excluded!, p-p scattering is the most plausible

Long-term RV trend ~10 m/s/yr is continuing

constraint on the mass and semi-major axis of ‘c’

First SEEDS paper

Further targetsover 10 misaligned planets have been discovered

eccentric planets and planets with long-term RV trend are also

interesting

currently no other group than SEEDS has a sufficient observing

time for all of these targets!

as is the case for the RM effect, numbers of groups would start

similar projects

Summary

RM measurements have discovered numbers of ‘tilted’ planets

tilted and/or eccentric planets are only explained by p-p

scattering or Kozai migration

RM measurements cannot distinguish between p-p scattering

and Kozai migration from spin-orbit alignment angles

Combination of direct imaging can resolve the problem

there are numbers of interesting targets to pinpoint a planetary

migration mechanism

SEEDS can become a pioneer of this study!

Many fruits will be harvested from the SEEDS tree!