David BrownAndrew 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

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.

3s

Barnes (2007)

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

2,121

5

3

18

11

'2

81

i

ii

i

i

i

efn

efa

R

M

M

Q

n

e

e

nefef

a

R

M

M

Q

n pp

p

s

ppp 43

32

'2

9

243

322 ~,min

'2

9

ss

ss

s

p

sss n

efefa

R

M

M

Q

n

Dobbs-Dixon et al (2004)

orb

sss

orb

pp

orb

ss

L

I

L

I

L

I

e

e

e

e

a

a2

2

2 ~,min

12

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

2,121

5

3

18

11

'2

81

i

ii

i

i

i

efn

efa

R

M

M

Q

n

e

e

nefef

a

R

M

M

Q

n pp

p

s

ppp 43

32

'2

9

243

322 ~,min

'2

9

ss

ss

s

p

sss n

efefa

R

M

M

Q

n

orb

sss

orb

pp

orb

ss

L

I

L

I

L

I

e

e

e

e

a

a2

2

2 ~,min

12

Dobbs-Dixon et al (2004)

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

2,121

5

3

18

11

'2

81

i

ii

i

i

i

efn

efa

R

M

M

Q

n

e

e

nefef

a

R

M

M

Q

n pp

p

s

ppp 43

32

'2

9

243

322 ~,min

'2

9

ss

ss

s

p

sss n

efefa

R

M

M

Q

n

orb

sss

orb

pp

orb

ss

L

I

L

I

L

I

e

e

e

e

a

a2

2

2 ~,min

12

Dobbs-Dixon et al (2004)

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

2,121

5

3

18

11

'2

81

i

ii

i

i

i

efn

efa

R

M

M

Q

n

e

e

nefef

a

R

M

M

Q

n pp

p

s

ppp 43

32

'2

9

243

322 ~,min

'2

9

ss

ss

s

p

sss n

efefa

R

M

M

Q

n

orb

sss

orb

pp

orb

ss

L

I

L

I

L

I

e

e

e

e

a

a2

2

2 ~,min

12

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◦ 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

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.

Hebb et al (2010)

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

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

Integration of MCMC median parameters

age ~ 3 Gyr

agegyro ~ 0.9 Gyr

Very close to Roche limit◦ tremain ~ 1 Myr

For same e0 and a0, range of Qs give compatible solutions.

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

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

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

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

Hellier et al (2009)

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

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.

Qs ~ 107 – 109

age ~ 0.4 – 1.5 Gyr

agegyro~ 0.4 Gyr

tremain ~ 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

pictureAre 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