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Ocean-Planets with CoRoT, Kepler & HARPS

Alain Léger et al. (CW10, 2006)

Ocean-Planets

new kind of telluric-like planets

Accretion: a > aice ( 4AU) ==> 50% ice +50% rocks (in mass)

+ migration ---> HZ: Ocean-Planet

closer: “Sauna-planet”

6 M Ocean-Planet

R / R = 2.00

1.63

6 M Rocky

Planet

Internal structure

~ jovian satellites

Rpl (Mpl)

can we discriminate OP / rocky P with:

COROT / Kepler (Rpl) + Doppler F-U (Mpl) ?

0

0,5

1

1,5

2

2,5

0 1 2 3 4 5 6 7 8

R / R_Earth

M / M_Earth

rockyrocky

Ocean-Planet

Earth

COROT

==> how small a can be ?

P = 50 days, GV

==> a = 0.27 AU

0.00

P (days)

0.00

Probability

0.10

OP fate when a

1. Swelling ?

P = P0 e-h/H, H = kT/ g ~ 15 - 20 km for = 18 (H2O not H2)

==> swelling not essential

P: 1 --> 103 bar (condensed) for h = [Ln(1000) - Ln(1)].H

~ 130 km for T= 600K << Rpl

e.g. 2 RE , h / Rpl = 1%

OP fate when a (2)

2. Atmosphere erosion by thermal escape

exosphere heating

by X, UX

a 0.05 AU ==> H2O should remain

0.01 a (AU) 0.10

life time (Gyr)

5 Gyr

energetic limit

plausible case

Fate when a (3)

3. Atmosphere erosion by stellar windcan be shown < thermal erosion

a 0.05 AU ==> most H2O should remain

Could COROT identify Ocean-Planets ?

Accuracy / Rpl & Mpl

<> = (3/4) M Rpl-3 Rpl = Rstar (F / F)1/2

€

σ1/ 3

ρ 1/ 3

⎛

⎝

⎜ ⎜

⎞

⎠

⎟ ⎟

2

= 1

3 σ MM

⎛

⎝ ⎜

⎞

⎠ ⎟

2

+ σ RstarRstar

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟

2

+ 1

2 σ ΔF /F

ΔF /F

⎛

⎝ ⎜

⎞

⎠ ⎟

2

uncertainties:

€

1/ 3

ρ 1/ 3 = 20.6 %model -->

a 2σ detection (95% confidence) ==>

€

σ1/ 3

ρ 1/ 3 ≤ 10.3 %

Accuracy / Rpl & Mpl (2)

€

σRstar

Rstar ≈ 5%(1)

==> 4%

Kepler ==> 0.4%

€

σF /F

2 ΔF /F Reference case: COROT mV = 12 Rpl = 2 RE

a = 0.10 AU

(2)

Accuracy / Rpl & Mpl (3)

€

13 σM

M(3)

==> 6.3 %

Doppler:

€

K = 0.09 Mpl

ME

a

1 AU

Mst

MSun

⎛

⎝ ⎜

⎞

⎠ ⎟ /m s

€

σK = σv

Nobs / 2

Reference case: HARPS (3.6 m) mV = 12 σv = 2 m/s (1h) t = 80 h (10 nights) a

maximum!

Combining uncertainties

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

11,5 12 12,5 13 13,5 14

m_v

(a) COROT + HARPS (3.6 m tel.)

Discrimination possible

Discrimination not possible

Mpl

= 10 MEarth

Mpl

= 6 MEarth

Combining uncertainties (2)

0

0,2

0,4

0,6

0,8

1

12 12,5 13 13,5 14

m_v

(b) Kepler + HARPS

Discrimination possible

Discrimination not possible

8 m tel.

3.6 m tel.

(Mpl = 6 M

Earth)

How many detections ?

- If all stars had 1 planet with 6 ME , 0.05 AU

==> 100 detections with possible discrimination OP/rocky P

- Conversely, 1 detection if 1%

(Some) CONCLUSIONS

• mV = 11 stars (weakly saturating) to be worked out

(if possible...)

• long Doppler integrations needed

• Kepler: new Doppler machine needed

co-workers

F. Selsis (1), B. Chazelas (2), P. Bordé(3), F. Bouchy(4), J-M Griessmeier(5), H. Lammer(6), C. Sotin (7), O. Grasset(7), D. Despois (8), D. Ehrenreich(4), M. Ollivier (2), F. Brachet(2), C. Moutou(9), M. Deleuil(9), P. Barge(9), J. Kasting(10), A. Labèque (2)

large number = some guaranty to avoiding errors ??