David Brown Andrew Collier Cameron, Leslie Hebb, Cassie Hall IAUS 276, Turin, 14/10/2010

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

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 Dobbs-Dixon et al (2004)

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

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

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

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 = 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

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 = Gyr  Planet ◦ P orb = 0.79 days ◦ a = ± ◦ e = 0.02±0.02 ◦ No alignment measurements to date. Hebb et al (2010)

Are falling planets spinning up their host stars? David Brown, IAUS 276, Turin, 14/10/2010

 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

 Q s ~ 10 5 – 10 6  Q p ~  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

 Star ◦ F6 ◦ T eff = 6400±100 K ◦ age = Gyr  Planet ◦ P orb = 0.94 days ◦ a = ± ◦ e = ± ◦ Well aligned (Triaud et al 2010)  λ=5.0 o Hellier et al (2009)

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

 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

 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

 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