1. COROT, COnvection, ROtation & Transits exoplanétaires
The CoRoT mission and Brown Dwarfs
Malcolm Fridlund

2. COROT: S/C 4.2m x 1.9m x 9.6m, 650kg, 530w Payload
CoRoTel, afocal, 27cm aperture, Baffle
CoRoTcam, dioptric, 4 CCD frame transfer 2048 x 4096
CoRoTcase, electronics box
Short observing runs (20d days) on asteroseismology fields
Up to 150 days on exo-fields

3. Objectives COROT has two design objectives:
- Searching for planets of a type similar to our own Earth
- Studying the inner parts of stars by measuring the changes in light output caused by acoustical sound waves travelling through the star.
COROT is essentially a very precise light-meter (photometer). COROT have measured changes in stellar flux of better than1 part in !
Can discriminate between colors ==> COROT can tell what the cause of variations in stellar flux is:
a) Intrinsic changes caused by activity or by waves travelling through the star
b) Occultations by a (small) planetary body passing in front of the star

4. Rp/R* = (DF)1/2 = ((Fno transit – Ftransit) / Fno transit)1/2
Light curve analysis: Solve for 5 unknown parameters: M*, R*, a, i and Rp  M* 1/3 / R* with 4 equations from the light curve and Kepler’s 3:rd law
Rp/R* = (DF)1/2 = ((Fno transit – Ftransit) / Fno transit)1/2
Kepler’s third law, the transit shape and transit duration  a, i, M*  R*  Rp
Under the following assumptions:
Planet orbit is circular (tend to be true for CoRoT objects)
Mp << M*
Stellar mass-radius relation is known (hmmm)
No ‘blends’
Planet has to enter fully the stellar disk (flat bottom LC) and a good period can be determined from the LC (long enough non-interupted lc which is the point with CoRoT).
e.g. Seager & Mallen-Ornelas, Ap.J., 585, 1038, 2003

5. Launched 27 Dec 2006; Operated since 15 Feb, 2007;
About light curves acquired;

10. Status – First we observed UFO’s
Both US ex-rockets and Chinese ex-satellites….
Now, forget asteroseismology….

11. How CoRoT planet detection works…
observations
data reduction
transit candidate list
Follow-up
observations
Confirmed planets
transit alarm!
 Preliminary candidate list
(large planets!)
basic data reduction
Follow-up
observations
Confirmed planets
Giant (and even small ones) planets can be detected already in „alarm mode“!

12. Close-in giant objects can be discovered in „alarm mode“
Very high S/N of data
transit events visible at N1 level
CoRoT-Exo-4b
For example:

13. Transiting planets around variable stars
„Discovery space“ for CoRoT
Transiting planets around variable stars
Observations made during the first „long run“ of CoRoT of 152 days duration
~ flux measurements with 512 s
(1. week) and then 32 s sampling
The star shows periodic variation over several days due to surface spots
The planet:
Period: days
Radius: / RJup
Mass: /-0.16 MJup
The star:
Type: G7
Magnitude: V=12.6 mag
Mass: /-0.06 Msun
Alonso et al. 2008

14. Small stuff is harder!
Lightcurve of 144d, demonstrating a rotation period of 22-23d
Raw light curve!
Cleaned and normalised 

15. Extracted light curves in color (top) and white light (bottom)

16. Lightcurve implies a planet but it can be a background object or a grazing occultation of a binary: Solved by photometry and spectroscopy
Photometry from the ground!
PSF of 7b

17. Spectroscopy of two kinds: Radial Velocities and high s/n, resolution spectrum for stellar parameters
Teff
Log g
[M/H]
Vmic
V sin i

18. ‚not many‘ Earth masses – 47 Jupiter masses
Results so far
About 20 planets/BD’s (2)
‚not many‘ Earth masses – 47 Jupiter masses
Periods between 0.85 and 96 days
High eccentricity in one case
5 more high probability targets
+ About 80 candidates – many to faint for HARPS/ VLT

19. Number 3!
CoRoT-Exo-3b
Looked ‘Jupiter-like’

20. 0.43% depth
Light curve analysis: Solve for 5 unknown parameters: M*, R*, a, I and Rp  M* 1/3 / R*

21. Transit on target!
High mass!

22. Deleuil et al, 2008, A&A, 491, 889 CoRoT-Exo-3b: P: 4.2568 d
r: RJ (0.07)
m: MJ (1.0)
r: 26.4 g cm-3 (5.6)
log g: 4.72 (0.07)
The star:
F3V
V = 13.3 mag
Teff = 6740K
V sin i = 17 km s-1
d = 680pc
1.37±0.09 Mo (lc+models)
R* = 1.56±0.09 RO (lc+models)
Age = 1.6 – 2.8 Gyr
Log g = 4.24±0.07 (models+spectra)
[M/H] = -0.02±0.06
Deleuil et al, 2008, A&A, 491, 889

23. Transiting planets p < 10d

24. Radius of 3b is 1 RJ just like theory says!
New BD, P ~ 16d, M ~ 47 MJ F-star
~ 10% (2 out of 20) of planets picked up by CoRoT are BD
< 5% of all exo-planets are BD (> 13 MJ)
For transiting planets: 5 most massive planets (our 2 + HAT-P-2b, WASP-14b and XO3b) orbit all around F-stars

25. Object
Spect.
P (days)
Mp (MJup)
[M/H]
WASP-14b
F5V
2.24
7.7
0±0.2
HAT-P-2 F8
5.63
9.09
0.14±0.08
WASP-18b F9
0.94
10.3
0±0.09
XO-3b
3.19
11.8
-0.17±0.08
CoRoT-3b
F3V
4.26
21.66±1.0
-0.02±0.06
CoRoT-? F
15.9
~ 47 ?

26. What now?
- CoRoT continues – probably for another 3 years but with half the FOV.
- KEPLER has produced its first results Demonstrates that they can detect 1 Earth radii. With this sensitivity, and their RV program they are going to pick up ~ same number of BD’s as CoRoT

28. The End
Public data:

29. Summary:
CoRoT have fulfilled design goals by discovering 7b
So far ~10 confirmed planets published or very close
Activity of stars is a surprise. Many objects turn out metal poor
Sun is not a ’normal, average’ star?

30. Amount of follow-up observations underestimated
– take significant effort and time. HARPS currently only instrument in the world that can detect Earth mass planets in RV
6. Will we find Earth-size planets soon? Yes!
- CoRoT, Kepler, microlensing, etc
7. Will we be able to confirm them soon? No! - not around solar analogue stars except in exceptional cases (non-HZ orbits)

31. The „first 4“! CoRoT-Exo-1b CoRoT-Exo-2b CoRoT-Exo-3b CoRoT-Exo-4b
P: d
r: RJ
m: 1.03 MJ
The star:
G0V
V = 13.6 mag
CoRoT-Exo-2b:
P: d
r: RJ
m: 3.31 MJ
The star:
K0V
V=12.6 mag
Alonso et al. 2008
Barge et al. 2008
CoRoT-Exo-3b
CoRoT-Exo-4b
CoRoT-Exo-3b:
P: d
r: RJ
m: MJ
The star:
G0V
V = 13.3 mag
CoRoT-Exo-4b:
P: d
r: RJ
m: 0.72 MJ
The star:
F0V
V=13.7 mag
Deleuil et al. 2008
Agrain et al. and Moutou et al