The long history of the Rossiter-McLaughlin effect and its recent applications
Simon Albrecht
Josh Winn, Teruyuki Hirano, Roberto Sanchis-Ojeda MIT
21 July 2011 Obliquity
Exoplanet systems: Close binary star systems:
Obliquity is a relic of formation and evolution Obliquity: Solar system
• The solar obliquity is 7◦
• The solar obliquity is only 7◦ ⇒ Evidence for formation in a single spinning disk (Laplace & Kant)
• The solar obliquity is not 0◦ ⇒ Early close encounter with another star? (Heller 1993) Exoplanets: two big surprises
Exoplanets can have high eccentricities and small semi-major axes
0.8
0.6
eccentricity 0.4
0.2
1 10 100 1000 period [days] data from www.exoplanets.org Exoplanets: two big surprises
0.8
0.6
eccentricity 0.4
0.2
1 10 100 1000 period [days]
• Whatever perturbs eccentricities may also perturb obliquities • Whatever causes orbital migration may also perturb obliquities • Planet disk migration → aligned orbital and stellar spins e.g. Lin et al. (1996), Cresswell et al. (2007) • Multi-body interaction → misaligned orbital and stellar spins e.g. Chatterjee et al. (2008), Fabrycky & Tremaine (2007) ⇒ Opportunity to learn about the formation of these systems How do close double stars form?
An old ”Hot-Jupiter problem”
We might expect good alignment: • Binary stars inherit common angular momentum and orientation from parent molecular cloud. • Even if originally misaligned, tidal interaction might align them (Hut 1981).
We might expect misalignment: • Chaotic star formation (Bate et al. 2010) • Third body, e.g. Kozai migration (Fabrycky & Tremaine 2007) H. R. Holt, Astronomy & Astro-Physics, XII, 646 (1893) The Rossiter-McLaughlin effect in β Lyrae and Algol
(Rossiter 1924; McLaughlin 1924, see also Schlesinger 1910) Observations during eclipse/transit
Independent estimate of v sin i? Observations during eclipse/transit
Independent estimate of v sin i? & projected obliquity Rossiter-McLaughlin effect: Snow White sleeping
Most people avoided the RM effect! Only a few went on and measured the RM effect. Mainly to obtain v sin i.
V1010 Oph
• Measurement of v sin i in 19 Algol systems, Twigg, PhD thesis (1979) • See also Hube & Couch (1982); Mochnacki & Doughty (1972)
(Worek et al. 1988) Rossiter-McLaughlin effect: exoplanets
HD 209458 b
JDB-2451000 (days) (Queloz et al. 2000) XO-3: misaligned
(Hebrard et al. 2008)
(Winn et al. 2009) Retrograde systems
WASP-17 HAT-P-7
Winn, Johnson, Albrecht et al. (2009) Narita, Sato, Hirano, & Tamura (2009) Anderson et al. (2010), Triaud et al. (2010) Bayliss et al. (2010) Results spring 2010
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proj. Obliquity [deg] 60
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4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] Results spring 2010: Period < 6 days (Hot-Jupiters)
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proj. Obliquity [deg] 60
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4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] RM measurements
Model predictions: center of gravity e.g. Hosokawa (1953); Kopal (1959); Sato (1974); Ohta et al. (2005); Gim´enez(2006)
We measure: some kind of CCF
Solutions: • Ignore • Forward modelling (Winn et al. 2005) • Include in the description (Hirano et al. 2010) • Calculate the change in stellar absortion lines directly (Albrecht et al. 2007, Cameron et al. 2009) RM measurements
What we expect We ignore: 20 What we measure • PSF spectrograph 10 ] • Stellar surface motion −1
(e.g. Gray 2005) 0 • Convective blueshift RM−effect [m s (Shporer & Brown 2011) −10 • Differential rotation • Star spots −20
−2 −1 0 1 2 Time RM measurements: out of transit data – Kepler 8
proj. obliquity: 26.4 ± 10.1 degrees (Jenkins et al. 2010)
• Star-spots • Undetected second planet • Long term stability spectrograph
⇒ out of transit data!
(Jenkins et al. 2010) RM measurements: Low SNR
WASP-2 +11 proj. obliquity: 153−15 degrees (Triaud et al. 2010) TrES-2 ] −1 proj. obliquity: −9 ± 12 degrees 50 (Winn et al. 2006) 0 PFS −50 HDS HARPS radial velocity [m s
0.188 0.304 40 20 0
] −20 −1 −40
0.188 0.304 40 20 0 −20 −40
0.188 0.304
−3 −2 −1 0 1 2
RM−effect [m s time [hr] ⇒ obliquity is undetermined (Albrecht et al. ApJ, in press, 2011) Results spring 2010: Period < 6 days (Hot-Jupiters)
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proj. Obliquity [deg] 60
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4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] Prediction for the following measurements ... (Winn, Fabrycky, Albrecht & Johnson 2010; see also Schlaufman 2010) HAT-P-4: cool aligned
(Winn et al. 2010) WASP-7: hot misaligned
] 100 −1
50 30 0 PFS ]
−50 -1 25
ailvlct [ms velocity radial −100 ]
−1 40 20 20 0 v sin i [kms 15 −20
eiul [ms residuals −40 −4 −2 0 2 -100 0 100 time [hr] proj. Obliquity [deg]
Albrecht et al. in prep (2011) WASP-24: cool aligned
Simpson et al. (2011) Results spring 2010
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proj. Obliquity [deg] 60
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4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] (Winn, Fabrycky, Albrecht & Johnson 2010) Results summer 2011
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proj. Obliquity [deg] 60
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4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] What can it mean?
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proj. Obliquity [deg] 60
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4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] • Does the planetary formation depend on stellar mass? • Does the planetary migration depend on stellar mass?
I Disk migration (alignment) I Multi body migration (misalignment) What can it mean?
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60 proj. Obliquity [deg]
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4500 5000 5500 6000 T eff[K] 6500 7000 7500 8000
] 0.04 • O 0.03
[M 0.02 CZ
M 0.01
4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] • Does the planetary formation depend on stellar mass? • Does the planetary migration depend on stellar mass? • Tidal realignment ? (Winn, Fabrycky, Albrecht & Johnson 2010) Obliquities in exoplanet systems: next steps
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60 proj. Obliquity [deg]
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4500 5000 5500 6000 T eff[K] 6500 7000 7500 8000
] 0.04 • O 0.03
[M 0.02 CZ
M 0.01
4500 5000 5500 6000 6500 7000 7500 8000 Teff [K] ⇒ Multi body migration? • Maybe stars are misaligned with disk? (e.g. Dong et al. 2010; Montgomery et al. 2010) • We could test this by using binary star systems. Close double stars BANANA Survey
Binaries Are Not Always Neatly Aligned
0.6
0.4 eccentricity 0.2
0.0 1 2 3 4 5 10 20 period [days] Poster F2 Rossiter-McLaughlin effect in double star systems Flux Flux Flux
Velocity Velocity Velocity Rossiter-McLaughlin effect in double star systems Rossiter-McLaughlin effect
(Struve & Elvey 1931) see also Albrecht et al. (2007) DI Herculis: an unsolved problem for 30 years
Measured apsidal motion is too slow (e.g. Martynov & Khaliullin 1980; Guinan & Maloney 1985; Claret 1998)
• B4 V and B5 V stars • Period = 10.55 days • e = 0.49 Apsidal motion: GR + tides + rotation expected
(Martynov & Khaliullin 1980; Guinan & Maloney 1985; Claret 1998) DI Herculis: Apsidal motion
• GR wrong? (Moffat 1984) However since early 80’s GR passed numerous tests. • Circumbinary planet? (Hsuan & Mardling 2006) • Misaligned spins? (Shakura 1984) Spectra Primary eclipse
1.00 0.95 0.90 intensity 0.85
4476 4480 4484 wavelength [Å] Primary eclipse
1.00 0.95 0.90 intensity 0.85
4476 4480 4484 wavelength [Å] Primary eclipse
◦ βp = 0
1.00 1.00 1.00
0.95 0.95 0.95 intensity intensity
0.90 0.90 0.90 intensity
0.85 0.85 0.85
4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484
1.00 1.00 1.00
0.95 0.95 0.95 intensity intensity
0.90 0.90 0.90 intensity
0.85 0.85 0.85
4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484
1.00 1.00 1.00
0.95 0.95 0.95 intensity intensity
0.90 0.90 0.90 intensity
0.85 0.85 0.85
4476 4480 4484 4476 4480 4484 4476 4480 4484 wavelength [Å] wavelength [Å] wavelength [Å] Primary eclipse
◦ βp = 72 ± 4
1.00 1.00 1.00
0.95 0.95 0.95 intensity intensity
0.90 0.90 0.90 intensity
0.85 0.85 0.85
4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484
1.00 1.00 1.00
0.95 0.95 0.95 intensity intensity
0.90 0.90 0.90 intensity
0.85 0.85 0.85
4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484 4476 4480 wavelength [Å] 4484
1.00 1.00 1.00
0.95 0.95 0.95 intensity intensity
0.90 0.90 0.90 intensity
0.85 0.85 0.85
4476 4480 4484 4476 4480 4484 4476 4480 4484 wavelength [Å] wavelength [Å] wavelength [Å] Results: apsidal motion
(Martynov & Khaliullin 1980; Guinan & Maloney 1985; Claret 1998) Results: apsidal motion
Albrecht et al. Nature (2009); see also Claret et al. (2010) ◦ NY Cephei: aligned βp = 2 ± 4
• Long period (15.3 days); • High eccentricity (e = 0.45)
1.0 1.0 1.0
0.9 0.9 0.9 intensity intensity
0.8 0.8 0.8 intensity
0.7 0.7 0.7
4460 4465 4470 Wavelength [Å] 4475 4480 4485 4460 4465 4470 Wavelength [Å] 4475 4480 4485 4460 4465 4470 Wavelength [Å] 4475 4480 4485
1.0 1.0 1.0
0.9 0.9 0.9 intensity intensity
0.8 0.8 0.8 intensity
0.7 0.7 0.7
4460 4465 4470 Wavelength [Å] 4475 4480 4485 4460 4465 4470 Wavelength [Å] 4475 4480 4485 4460 4465 4470 Wavelength [Å] 4475 4480 4485
1.0 1.0 1.0
0.9 0.9 0.9 intensity intensity
0.8 0.8 0.8 intensity
0.7 0.7 0.7
4460 4465 4470 4475 4480 4485 4460 4465 4470 4475 4480 4485 4460 4465 4470 4475 4480 4485 Wavelength [Å] Wavelength [Å] Wavelength [Å]
(Albrecht et al. 2011b) ◦ CV Velorum: misaligned βp = −42 ± 10
• Short period (6.9 days); • circular orbit (e = 0)
10 aligned model ]
−1 5
0
−5 RM [kms effect
−10
−10 −5 0 5 10 Time [hr] (Albrecht et al. in prep. 2011) Conclusions Rossiter-McLaughlin effect: Essential modeling tool to obtain stellar obliquity ⇓ • A pattern in the proj. obliquities is emerging for hot-Jupiters • Indication on formation and migration? • Will be refined for low mass, long period and multiple planet systems
• DI Herculis problem solved • Misalignment might not be uncommon • Alignment seems not to be a simple function of period or eccentricity