Exoplanet Working Groups

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Exoplanet Working Groups

• CoRoT Brazil Workshop
• Natal 2004 oct 29th nov 2th

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• Summary on exoplanet discoveries
• Challenge on the terrestrial planets and the
  place of CoRoT
• Present organizing of the Exo WG

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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 lt e lt 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

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Mass/period segregations
Min-mass/period ? R single dwarf
stars (binaries and evolved removed) ? heavy
planets ( gt2 ) ? intermediate (0.75 gt lt2 ) ?
light planets (lt 0.75 )
Orbital period distribution -red heavy
-grey light (lt0.75)
(After Udry et al. 2003)
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Parent star metallicity
(After Santos et al. 2003)
? Signature of the core instability scenario ? ?
Result of engulfed migrating planets ?
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Summary on Giant Planets

• Commonly form around stars (single or binaries)
• Have masses in a wide range (0.6 lt m lt 10 mJup )
• Can be found in the inner part of the system
• Can have orbits with very large eccentricities
• ? Strong differences with our Solar System
• We still do not know how do they form !
• Core instability in a layered nebula
• Gravitational instability in a gas nebula

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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 consensus Final stage
Embryos ? T. Planets Depends on the presence and
location of G. planets !
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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 required
• CoRoT 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

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ExoplanetsTwo Working Groups

• E.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. Magalis talk

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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 !
• Strategy
• ?Brain storming during Planet workshops
• ? Specific works decided during Exo sessions at
  CWs

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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

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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

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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? )

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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

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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

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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

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Conclusions of PW3

• PW3 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
  !

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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