Travis Metcalfe (SSI)

Asteroseismology of Kepler Exoplanet Host Stars

1992: first pulsar planets

3 planet system

2 = 4 x Earth mass

1 = 2 x Moon mass

Orbits closer than Mercury

1995: first radial velocity planet

0.5 x Jupiter mass

Orbit closer than Mercury

2001: first transiting planetOrbit closer than Mercury

Size near Jupiter

Exoplanet atmospheres

Detections

- Sodium

- Carbon monoxide

- Water vapour

2004: first microlensing planet

Hosted by a tiny red dwarf

Orbit size similar to Mars

Mass similar to Jupiter

Mass = 3 x Jupiter

Orbit size = 3 x Neptune

Host star mass = 2 x Sun

2008: first direct image

2010: first habitable planet?

Gliese 581g

Mass = 3 x Earth

Orbit size = 0.4 x Mercury

Host star mass = 0.3 x Sun

Higher temperature = faster sound speed

Lighter gases = faster sound speed

Global oscillation properties

Elsworth & Thompson (2004)

max

Scaling relations

Mathur et al. (2012)

Grid-based methods

Mathur et al. (2012)

Fitting the frequencies

Metcalfe et al. (2012)

• Stellar evolution tracks from ASTEC, pulsation analysis with ADIPLS

• Parallel genetic algorithm optimizes globally, local analysis + SVD for errors

• Stellar age from match to large separation, correct surface effects empirically

0.75 < M < 1.75

0.002 < Z < 0.05

0.22 < Y < 0.32 1.0 < < 3.0

Metcalfe et al. (2009), Woitaszek et al. (2009)

http://amp.ucar.edu/

Chaplin et al. (2011, Science)

Asteroseismic Modeling Portal

Kepler-21: a love story

Howell et al. (2012)

• 1.64±0.04 Re planet in a 2.8-day orbit around an oscillating F subgiant

• Asteroseismic target prior to exoplanet discovery, expanded collaboration

• radius (1.86±0.04 R), mass (1.34±0.06 M), age (2.84±0.34 Gyr)

Kepler-22: habitable super-Earth

Borucki et al. (2012)

• 2.38±0.13 Re planet with 290-d orbit in habitable zone of G5 host star

• Spectroscopy and global oscillation properties for grid-based modeling

• radius (0.98±0.02 R), mass (0.97±0.06 M), age (~4 Gyr?)

Kepler-36: formation puzzle

Carter et al. (2012, Science)

Kepler-36: formation puzzle

• 1.5 and 3.7 Re planets in 13.8-d and 16.2-d orbits (7:6 period ratio)

• Asteroseismology and transit timing variations yield planet densities

• Super-Earth and Neptune (8:1 density ratio) in neighboring orbits. How?

Carter et al. (2012, Science)

Kepler-##: smallest exoplanet

Barclay et al. (submitted)

• 0.28 / 0.8 / 2.1 Re planets in 13 / 21 / 39 day orbits (no TTVs yet detected)

• radius (0.77±0.02 R), mass (0.80±0.04 M), age (~6 Gyr)

• Innermost planet is smaller than Mercury (similar to size of Moon)

Future prospects

• Longer data sets will resolve mode splitting, providing independent constraints on rotational inclination and spin-orbit alignment.

• Extended time series will probe variations due to magnetic cycles, and provide statistics on stellar super-flares (with implications for habitability).

• Comparison with control sample of stars without known planets may reveal correlations between stellar composition and occurrence of planets.