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Are falling planets spinning up their host stars?

Are falling planets spinning up their host stars?. David Brown Andrew Collier Cameron, Leslie Hebb, Cassie Hall. IAUS 276, Turin, 14/10/2010. Aims. Can we use gyrochronology to reliably estimate the ages of exoplanet systems?

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Are falling planets spinning up their host stars?

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  1. Are falling planets spinning up their host stars? David Brown Andrew Collier Cameron, Leslie Hebb, Cassie Hall IAUS 276, Turin, 14/10/2010

  2. Aims • Can we use gyrochronology to reliably estimate the ages of exoplanet systems? • Do tidal interactions affect the natural spin down of exoplanet host stars? • Can we constrain Q’s and Q’p through modelling tidal interactions? Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  3. Gyrochronology • Magnetic braking caused by stellar wind • Weber & Davis (1967) • Rotation period can be used as a proxy for age. Barnes (2007) Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  4. Tides Dobbs-Dixon et al (2004) Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  5. Tides Dobbs-Dixon et al (2004) Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  6. Tides Dobbs-Dixon et al (2004) Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  7. Tides Dobbs-Dixon et al (2004) Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  8. Methodology • Integrate equations forward in time from a set of parameters at some time in the past. • Initial conditions • Ωp = n • t0 = 0.150 Gyr • Ωs scaled from P – (J-K) relation for Coma-Berenices cluster(Collier Cameron et al, 2009) • Evaluation • At each time step, calculate fit to observed parameters • Add prior on stellar age from isochrones Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  9. WASP-19: System • Hebb et al (2010) • Star • Late G-dwarf • Teff = 5500±100 K • [M/H] = 0.1±0.1 • age = 5.5+9.0-4.5 Gyr • Planet • Porb = 0.79 days • a = 0.0164±0.0005 • e = 0.02±0.02 • No alignment measurements to date. Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  10. WASP-19: Grid Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  11. WASP-19: MCMC Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  12. WASP-19: Rotation Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 • Integration of MCMC median parameters • age ~ 3 Gyr • agegyro ~ 0.9 Gyr • Very close to Roche limit • tremain ~ 1 Myr • For same e0 and a0, range of Qs give compatible solutions.

  13. WASP-19: Rotation • Qs ~ 105 – 106 • Qp ~ 104 - 109 • All imply that WASP-19b is in infall. • All give very short remaining lifetimes. Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  14. WASP-18: System Hellier et al (2009) • Star • F6 • Teff = 6400±100 K • age = 0.630+0.950-0.530 Gyr • Planet • Porb = 0.94 days • a = 0.02026±0.00068 • e = 0.0092±0.0028 • Well aligned (Triaud et al 2010) • λ=5.0o +3.1-2.8 Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  15. WASP-18: Grid Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  16. WASP-18: MCMC Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  17. WASP-18: Rotation Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 Median MCMC parameters imply WASP-18b on verge of infall. Short remaining lifetime Older than gyrochronology suggests.

  18. WASP-18: Rotation Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 • Range of solutions give range of histories. • Qs ~ 107 – 109 • age ~ 0.4 – 1.5 Gyr • agegyro~ 0.4 Gyr • tremain ~ 0.06 – 5 Gyr

  19. Conclusions • Tidal interactions with hot Jupiters can have a strong effect on stellar rotation. • Host stars will rapidly spin up during the final stages of infall. • Effect is observable. • Gyrochronology is a useful tool, but should not be trusted absolutely for hot Jupiter hosts • WASP-19 much older, in line with isochrones. • WASP-18 could be much older, but still uncertain. • Q not universal. • Different systems can have completely different ranges of values. • Affects timescale of evolution, but not the overall picture Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

  20. References • Barnes S. A., 2007, ApJ, 669, 1167 • Collier Cameron A. et al., 2009, MNRAS, 400, 451 • Dobbs-Dixon I., Lin D. N. C., Mardling R. A., 2004, ApJ, 610, 464 • Eggleton P. P., 1983, ApJ, 268, 368 • Hebb L. et al., 2010, ApJ, 708, 224 • Hellier C. et al., 2009, Nature, 460,1098 • Skumanich A., 1972, ApJ, 171, 565 • Weber E. J., Davis Jr. L. 1967, ApJ, 148, 217 Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

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