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

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 -- 60 days) on asteroseismology fields Up to 150 days on exo-fields

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 1 000 000! 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

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

Launched 27 Dec 2006; Operated since 15 Feb, 2007; About 80000 light curves acquired;

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

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“!

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:

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 ~369000 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: 1.742996 days Radius: 1.465+/-0.029 RJup Mass: 3.31+/-0.16 MJup The star: Type: G7 Magnitude: V=12.6 mag Mass: 0.97+/-0.06 Msun Alonso et al. 2008

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

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

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

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

‚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

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

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

Transit on target! High mass!

Deleuil et al, 2008, A&A, 491, 889 CoRoT-Exo-3b: P: 4.2568 d r: 1.01 RJ (0.07) m: 21.66 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

Transiting planets p < 10d

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

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 ?

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

The End Public data: http://idoc-corot.ias.u-psud.fr/

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?

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)

The „first 4“! CoRoT-Exo-1b CoRoT-Exo-2b CoRoT-Exo-3b CoRoT-Exo-4b P: 1.5089557 d r: 1.49 RJ m: 1.03 MJ The star: G0V V = 13.6 mag CoRoT-Exo-2b: P: 1.742996 d r: 1.465 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: 4.2568 d r: 1.01 RJ m: 21.66 MJ The star: G0V V = 13.3 mag CoRoT-Exo-4b: P: 9.20205 d r: 1.19 RJ m: 0.72 MJ The star: F0V V=13.7 mag Deleuil et al. 2008 Agrain et al. and Moutou et al. 2008