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David Brown Andrew Collier Cameron, Leslie Hebb, Cassie Hall IAUS 276, Turin, 14/10/2010
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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
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Magnetic braking caused by stellar wind Weber & Davis (1967) Rotation period can be used as a proxy for age. Barnes (2007)
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 Dobbs-Dixon et al (2004)
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 Dobbs-Dixon et al (2004)
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 Dobbs-Dixon et al (2004)
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 Dobbs-Dixon et al (2004)
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 Integrate equations forward in time from a set of parameters at some time in the past. Initial conditions ◦ Ω p = n ◦ t 0 = 0.150 Gyr ◦ Ω s 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
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010 Star ◦ Late G-dwarf ◦ T eff = 5500±100 K ◦ [M/H] = 0.1±0.1 ◦ age = 5.5+9.0-4.5 Gyr Planet ◦ P orb = 0.79 days ◦ a = 0.0164±0.0005 ◦ e = 0.02±0.02 ◦ No alignment measurements to date. Hebb et al (2010)
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010
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Integration of MCMC median parameters age ~ 3 Gyr age gyro ~ 0.9 Gyr Very close to Roche limit ◦ t remain ~ 1 Myr For same e 0 and a 0, range of Q s give compatible solutions. Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010
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Q s ~ 10 5 – 10 6 Q p ~ 10 4 - 10 9 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
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Star ◦ F6 ◦ T eff = 6400±100 K ◦ age = 0.630+0.950-0.530 Gyr Planet ◦ P orb = 0.94 days ◦ a = 0.02026±0.00068 ◦ e = 0.0092±0.0028 ◦ Well aligned (Triaud et al 2010) λ=5.0 o +3.1-2.8 Hellier et al (2009)
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Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010
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Median MCMC parameters imply WASP- 18b on verge of infall. Short remaining lifetime Older than gyrochronology suggests. Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010
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Range of solutions give range of histories. Q s ~ 10 7 – 10 9 age ~ 0.4 – 1.5 Gyr age gyro ~ 0.4 Gyr t remain ~ 0.06 – 5 Gyr Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010
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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
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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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