CoRoT-Brazil Pierre BARGE

Exoplanet Working Groups

CoRoT Brazil WorkshopNatal 2004 : oct 29th – nov 2th

CoRoT-Brazil

• Summary on exoplanet discoveries• Challenge on the terrestrial planets

and the place of CoRoT• Present organizing of the Exo WG

CoRoT-Brazil

Exoplanet search main results

(RV from 1995 to 2004)• 7% of dwarf stars around Sun host giant planets (EGP)• Stars with planets have spectral types from F to M• Statistical studies become possible ( 130 EGPs)• EGP are preferentially found around metal-rich stars• Orbital periods range from ~1.5 days to some years• Large eccentricities are common ( 0 < e < 0.927)• Planet masses range from 14M to 10MJup • Mass distribution peaks toward small planets• Density of the planets is determined in some cases• 10 multi-planets discovered (some commensurabilities)• Some planets are found in binary star systems

CoRoT-Brazil

Mass/period segregations

(After Udry et al. 2003)

Min-mass/period

R: single dwarf stars(binaries and evolved * removed)

● heavy planets ( >2 )○ intermediate (0.75 > ; <2 ) ∆ light planets (< 0.75 )

Orbital period distribution -red: heavy -grey: light (<0.75)

CoRoT-Brazil

Parent star metallicity

(After Santos et al. 2003)

Signature of the core instability scenario ? Result of engulfed migrating planets ?

CoRoT-Brazil

Summary on Giant Planets– Commonly form around stars (single or

binaries)– Have masses in a wide range (0.6 < m <

10 mJup )– Can be found in the inner part of the system– Can have orbits with very large

eccentricities

Strong differences with our Solar SystemWe still do not know how do they form !

• Core instability in a layered nebula • Gravitational instability in a gas nebula

CoRoT-Brazil

About terrestrial planets– Well defined problem adressed in terms of

kinetic equations and numerical simulation, both.

– The standard formation scenario is accretion by planetesimal accumulation (Safronov 1969)Planetesimals moon sized bodies (105 yrs)

or bigger planetary embryos Good agreement and common consensusFinal stage: Embryos T. PlanetsDepends on the presence and location of G. planets !

CoRoT-Brazil

Close-in terrestrials: a very “hot” question

• Planets with mass similar to that of Uranus were recently discovered by RV method (14 – 20 m)

• Are they Uranus like (migrated/evaporated) or big terrestrial ?

Their density (radius) is requiredCoRoT will permit:

• To answer the above question • To discover other such planets• To test a number of emerging models• To start statistics of terrestrial planets …

CoRoT-Brazil

Exoplanets:Two Working GroupsE.W.G.

(Exoplanet Working Group)

Coordination of sci. activities • Transit detection• Stellar “noise”• Works on specific topics (planetary formation, physics of

Gas Giants, atmospheres and wind, magnetosphere, tidal effect, dynamical stability, planets in binaries, …)

E.C.O.W.G.(Exo. Complementary Obs. WG)

Coordination of obs. Effort• Preparatory observations• Follow-up• Complementary observations• … …• Scientific data base (Exodat)

Cf. Magali’s talk

CoRoT-Brazil

E.W.G.Objectives and Strategy

• Objectives– To optimize the impact of CoRoT data on exoplanetary

science– To organize the scientific activity in various working teams– To make people work together– To stimulate exchanges between seismo and exo

communities (stellar activity as a noise, metallicities and spectral types, ….)

The difficulty lies in beginning to work with no data …!

• StrategyBrain storming during PPlanet workshops Specific works decided during Exo sessions at CWs

CoRoT-Brazil

The Planet Workshops• PW1: “Planetary formation: toward a new scenario”

(june 2-3 2003):

• PW2: “Planetary transit detection: stellar noise and false alarms” (dec 8-9 2003):

• PW3: “Close-in exoplanets: the star-planet connection” (may 13-14 2003):

• PW4: “Automatic Spectral Classification for large data sets” (reported)

• PW5: … to be defined at the next CoRoT Week in Granada

CoRoT-Brazil

Some specific works • Simulation of the stellar activity

Two different approaches:– Rotational modulation by dark spots and active

regions calibrated on Virgo-Soho data– Microvariability deduced from a spectral analysis

of Sun variations• Simulation of light-curves and transits

• Blind test of the detection algorithms using simulated light-curves

CoRoT-Brazil

Points raised at PW2on transit detection

• How to compare and merge the capabilities of the various methods ?

• How to build up again a detected transit ? (least square fitting, Bayesian,….)

• Estimate others false alarms possibilities• How to face stellar noise ?

Appropriate filtering ….. Use of colors (CoRoT, Eddington? )

CoRoT-Brazil

Main conclusions of PW2• Eclipsing binaries

– probably one of the main sources of confusion – also good targets for planet search !

• Radial velocity follow up– Not a method to remove false alarms – Can remove confusing situations– Adds important information (mass)

• Testing detection algos. would require working on the same light-curves and blindly Proposal: Free exchanges of light-

curves between the various teams

CoRoT-Brazil

Detecting transit blindly (1st test – CW5)

This test involved various teams in our groups (initiated during CW5):

• To produce simulated light-curves which account for:– Instrumental noises– Noises from the stellar variability– Planetary and stellar signals (possible ambiguities)– A sample of 1000 LCs were produced (secret: 1 person)

• To look for possible transits using different detection algorithms – Five different teams were involved (open to all CoIs)– To work on a common set of LCs for relevant

comparisons

CoRoT-Brazil

Conclusions of 1st blind test• Very different detection methods tested• False detections seem specific to the algo. used• Stellar micro-variability is not the main limitations• The method used to detrend the signal is almost as

important as the detection algorithm itself• In some cases detrending can produce artefacts• Background eclipsing binaries are source of confusion• Characterization of the transits requires other analysis

of the signal• CoRoT detectivity limitation:

(1.1 R 3days) on M0 dwarf stars

Results are to be published and LCs will be available on request

CoRoT-Brazil

Conclusions of PW3PW3 was devoted to the Close-in Exosolar planets and

the relations they have with the host star.• A lot of interesting points were addressed:

– Existence of extremely hot giant planets (3 confirmed)– Evaporation rate of hot jupiter planets is strong– Origin of the overmetallicity of stars (primordial or not?)– How such planet form ? Migration ?– Relations with the host star

(tidal effect, radiative and magnetic interactions)– Possible existence Hot Uranus, big rocky planets

(primordial or evaporated remnants), big liquid planets, ….

Many questions CoRoT will help to solve soon !

CoRoT-Brazil

Next work within EWG

To detect transit blindly using 3-color lcs• This test will involve the detection teams of EWG• LCs will be simulated using the instrument-model

(M.Auvergne) to account for realistic noises• Transits and ambiguities will be included as in the

first blind test• This will be a good opportunity to test how color

information can improve CoRoT detection capabilities