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Subaru Measurements of the Rossiter-McLaughlin Effect and
Direct Imaging Observations for Transiting Planetary Systems
Norio Narita
National 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 Satellites
 Asteroids
 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
Snow line
Jupiter
Need planetary migration mechanisms!
Standard Migration Models
Type I and II migration mechanisms
 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
Eccentricity Distribution
Eccentric
Planets
Jupiter
Cannot be explained by Type I & II migration model
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
Misaligned and even retrograde planets are predicted.
0
30
60
90
120
150
180 deg
Nagasawa, Ida, & Bessho (2008)
How can we test these models by observations?
Planetary transits
transit in the Solar System
transit in exoplanetary systems
(we cannot spatially resolve)
2006/11/9
transit of Mercury
observed with Hinode
slightly dimming
If a planetary orbit passes in front of its host star by chance,
we can observe exoplanetary transits as periodical dimming.
The Rossiter-McLaughlin effect
When a transiting planet hides stellar rotation,
star
planet
planet
the planet hides the approaching side
the planet hides the receding side
→ the star appears to be receding
→ the star appears to be approaching
radial velocity of the host star would have
an apparent anomaly during transits.
What can we learn from RM effect?
The shape of RM effect
depends on the trajectory of the transiting planet.
well aligned
misaligned
Radial velocity during transits = the Keplerian motion and the RM effect
Gaudi & Winn (2007)
Observable parameter
λ： sky-projected angle between
the stellar spin axis and the planetary orbital axis
(e.g., Ohta+ 2005, Gaudi & Winn 2007, Hirano et al. 2010)
Previous studies
1.
HD209458
Queloz+ 2000, Winn+ 2005
2.
HD189733
Winn+ 2006
3.
TrES-1
Narita+ 2007
4.
HAT-P-2
Winn+ 2007, Loeillet+ 2008
5.
HD149026
Wolf+ 2007
6.
HD17156
Narita+ 2008,2009, Cochran+ 2008, Barbieri+ 2009
7.
TrES-2
Winn+ 2008
8.
CoRoT-2
Bouchy+ 2008
9.
XO-3
Hebrard+ 2008, Winn+ 2009, Narita+ in prep.
10. HAT-P-1
Johnson+ 2008
11. HD80606
Moutou+ 2009, Pont+ 2009, Winn+ 2009
12. WASP-14
Joshi+ 2008, Johnson+ 2009
13. HAT-P-7
Narita+ 2009, Winn+ 2009
14. CoRoT-3
Triaud+ 2009
15. WASP-17
Anderson+ 2009
16. CoRoT-1
Pont+ 2009
17. WASP-3
Simpson+ 2010, Tri?+ 2010
18. Kepler-8
Jenkins+ 2010
19. TrES-4
Narita+ 2010
20. HAT-P-13
Winn+ 2010, Hirano+ in prep.
Red: Eccentric
Blue: Binary
Green: Both
and more and more
Subaru Radial Velocity Observations
HDS
Subaru
Iodine cell
Prograde Planet: TrES-1b
Our first observation with Subaru/HDS
NN et al. (2007)
We confirmed a prograde orbit and
the spin-orbit alignment of the planet.
Ecctentric Planet: HD17156b
Eccentric planet with the
orbital period of 21.2 days.
NN et al. (2009a)
λ = 10.0 ± 5.1 deg
Well aligned in spite of its eccentricity.
Possibly Binary System Planet: TrES-4b
NN et al. 2010a. λ = 6.3 ± 4.7 deg
NN et al. in prep.
Well aligned in spite of its binarity.
Retrograde Exoplanet: HAT-P-7b
NN et al. (2009b)
Winn et al. (2009)
More Retrograde Exoplanets
Queloz et al. (2010)
WASP-8b
WASP-17b
Triaud et al. submitted
WASP-15b
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
Motivation
 Spin-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 Project
 SEEDS: 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)
Winn et al. (2009)
2007 and 2009 Keck data
2008 and 2010 Subaru data
HJD - 2454000
very interesting target for direct imaging observation!
Observation and Analysis
 Subaru/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
N
E
Left: Subaru HiCIAO image, 12’’ x 12’’, Upper Right: HiCIAO LOCI image, 6’’ x 6’’
Lower Right: AstraLux image, 12’’ x 12’’
Characterization of binary candidates
projected separation: ~1000 AU
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.
Constraints on outer bodies
H band contrast ratio
5σ detectable mass
 Contrast: [email protected]'’(100AU), [email protected]'’(160AU), [email protected]'’(320AU)
 Corresponding 5σ detectable mass: 110 MJ, 80 MJ, 70 MJ
 massive planets and brown dwarfs were not excluded at this point
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
Kozai migration forbidden
boundary
Kozai migration allowed
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)
Possible additional planet ‘HAT-P-7c’
Winn et al. (2009c)
2007 and 2009 Keck data
2008 and 2010 Subaru data
HJD - 2454000
Long-term RV trend ~10 m/s/yr is continuing
constraint on the mass and semi-major axis of ‘c’
Kozai migration excluded!, p-p scattering is the most plausible
First SEEDS paper
Further targets
 over 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!