tidal dynamics of transiting exoplanets dan fabrycky uc santa cruz 13 oct 2010 photo: stefen seip,...
TRANSCRIPT
Tidal Dynamics of Transiting Exoplanets
Dan Fabrycky
UC Santa Cruz
13 Oct 2010
Photo: Stefen Seip, apod/ap040611
At: The Astrophysics of Planetary Systems: Formation, Structure, and Dynamical Evolution
Tidal Dynamics of Transiting Exoplanets
Why tides?
Cumming+08
Hot Jupiters are a Sub-class
Why transits?1) mp, Rp, (ap/R*) 2) /
Period (days)
Mas
s [M
J]
Dynamics not foreseen?{Spin-orbitmigration (Queloz+2000)
TTV/TDV (Miralda-Escude 2002)
Tidal consumption (Sasselov 2003)
Pont et al. 2010
• Historic perspective: disk migration is destructive (Goldreich & Tremaine 1980, Ward 1997)
• Stop it near the star? (Lin et al. 1996)
That gives >10x too many hot Jupiters (Ida talk)
• Solution: Disk migration does not produce most hot Jupiters.
Disk migration?
Cumming+08
Alternative: tidal dissipation
Rasio & Ford 1996, Wu & Murray 2003,
Matsumura, Peale, & Rasio 2010
Kozai Movie
QuickTime™ and a decompressor
are needed to see this picture.
But will tidal heating destroy the planet?
Disruption possible (Et>Eb) for
Maximum tidal input:
Planet binding energy:
work in progress with Doug Lin & Tsevi Mazeh
Circularization with Overflow…In Words
• Dynamics slowly lowers the periapse• Circularization takes hundreds of orbits• The planet inflates slowly to the Roche Lobe
• It overflows gently through L1 while circularizing
• Transfer of angular momentum raises periapse
In equations
• Energy conservation
• A.M. conservation
• Roche-Lobe filling
In a picture
Circularization with Overflow
• Allows the survival of tidally migrating/inflating planets
• May explain Mp-P correlation (Mazeh et al. 2005 relation):
Lower mass planets
less binding energy
overflow more back away from the star further
• This model is doomed to succeed.
Inclination expectations
remain aligned
get misaligned
Inclination to stellar equator?
• Disk migration
• Kozai cycles with tidal
friction
• Planet-planet scattering with
tidal friction
Fabrycky & Tremaine 07Wu+07
Nagasawa+08
e.g., Cresswell+07
Also, resonant-pumping (Yu & Tremaine 01, Thommes & Lissauer 03)
Inclination expectations
Comparison to Observations
Kozai
Planet-PlanetScattering
observations(Triaud+10)
New Correlations
• Host’s convective zone mass
• Tidal torque
Winn, Fabrycky, Albrecht, Johnson 2010 (see also Schlaufman 2010)
Clear and Present Danger:Planetary Consumption
• Tidal calculations assuming only the convective envelope feels torque from the planet.
• The planet can realign the star’s observable photosphere.
• The photosphere is not spun-up, due to magnetic braking.
• The planet is doomed.
Let’s look to Astrophysics
Radiative-Convective Decoupling
• Decoupling was predicted theoretically (Pinsonneault+1987)
• Observed stellar rotation periods as a function of age suggest decoupling (e.g., Irwin & Bouvier 2009)
• BUT: Coupling apparently observed in the Sun
Howe 2009, from helioseismology
[
10-4 r
ad/s
]
r/Rstar
Conclusions
• Fundamental indicators of hot Jupiter formation:– The pile-up and the mass-period relation within it– Spin-orbit alignment statistics and correlations
• Circularization from high eccentricity is likely the dominant channel.
• Tides in the star might damp obliquities, but it is time to entertain a variety of ideas.
Theory of Secular Resonance
frequency g
frequency
i
HD 80606:
Secular Resonance during Kozai cycles with tidal friction