Diapositive 1

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How many transiting planets will we find ?
F. Fressin, M. Barbieri, T. Guillot, F. Pont, L.
Nesta Exeter, September 15, 2008
Observatoire de la Côte dAzur,
Nice fressin_at_oca.eu
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Where are the known planets ?
Dec
0
360
RA
RV surveys 7.7 9.5
XO 9.8 12.1 SWASP 9.8 12.7 TrES
11.6 12.4 HATnet 10.4 12.6
CoRoT 12.6 14.0
OGLE 15.5 17.0
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Magnitude of host stars ?
(May 2008)
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Statistical study of transit surveys
I Short description of the model II What can
we do with the number of giant planets we have
? III Whats left to discover ? up to which
magnitude is it worth searching ? IV CoRoT and
10-3 photometry V What will we get from
M-dwarfs ? VI What will we get in the near
future ? Where should we stress ?
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CoRoTlux A statistical tool to simulate transit
surveys
Generate a stellar field
Add companions
Calculate the radius of the planets
Estimate which transiting object is detectable
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CoRoTlux A statistical tool to simulate transit
surveys Hypotheses
From Besancon model (Robin et al. 2003)
Stellar counts Color magnitude diagrams

• Stellar fields
• Giant planets
• Fields of view / observation windows / white and
  red noise levels / detection threshold

• From radial velocity discoveries
• Distribution of Fe/H
• - Planet occurrence vs. Fe/H
• Mass vs. Period carbon copies of RV planets
  VHJ added
• (includes potential correlation Mazeh et al.
  2002)
• Simple evolution model (Guillot et al. 2006)

• (Fischer Valenti 2005 Santos et al. 2006)

From light curves study
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How many planets do we need ? Do we need numbers
or precision ?

• Understand planetary distribution and formation
  (and evolution, migration )
• For giant planets
• Core mass, internal energy source,
  recirculation, tidal effects
• gt Need for numbers and precision in
  characteristics measurement
• Atmospheric composition
• gt Need for high-precision spectro-photometry
• For smaller planets
• huge space for parameters variety of
  composition and layers
• gt Need for extra precision, mass, radius
  measurement and spectroscopy.
• HST and Spitzer are just enough to get an idea of
  the spectrum for what could be the brightest
  exoplanet are we sure that well be able to do
  anything with earth-mass planets, even with JWST
  ? At least, we need the best targets !

How many ? What can we already do ?
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What can we do with numbers ? Statistically test
formation models

• 7 parameters Planet (Mass, radius, period, Teq)
  and Star (Mass, Radius, Teff,Fe/H) that may be
  linked together
• and their combinations

Results of our study of ground based surveys
(Fressin et al, 2008)
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Results of the logit multi-variable analysis
Nominal model
Rp x 1.1
40 transiting planets are already enough to
completely rule out what looked like to be a
marginal mistake in the model !
Probability of 76 to reproduce the
characteristics of known Pegasids only 0.02
if we introduce an error by multiplying
simulated planets radii by 1.1
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Results Mass-radius diagram
Mass vs. Radius Teff vs. Radius Surface
gravity vs. Period
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Results
Mass vs. Radius Teff vs. Radius Surface
gravity vs. Period
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Results
Mass vs. Radius Teff vs. Radius Surface
gravity vs. Period (Noyes 2005)
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How many planets will we find ?
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How many dwarf stars for one transiting giant
planet?

• 5.9 1.2 of F-G-K dwarf stars in solar local
  neighborhood host a Giant Planet (0.3 to 15 MJup
  within 4 AU)
• (from Fischer-Valenti 2005, Santos et al. 2006)
• There is 1 giant planet for 17 3 F-G-K dwarf
  stars
• 9.1 1.8 of giant planets are Pegasids (period
  between 1 and 5 days)
• (from Fischer-Valenti 2005, Santos et al. 2006)
• There is 1 Pegasid for 186 40 F-G-K dwarf stars
• There is 1 transiting giant planet for 1350 350
  F-G-K dwarf stars
• (CoRoTlux simulation at least 1 transit in 1
  year including grazing planets)
• Then you need to detect them !

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How many F-G-K dwarf stars per magnitude?

• Number of stars per magnitude
• Tycho 2 (Hyparcos) catalog considered 99
  exhaustive up to magnitude 11
• 2Mass catalog up to magnitude 14.5
• Hubble guide star catalog and extrapolations for
  higher magnitudes

• Stellar type determination
• From Mauro Barbieris dedicated analysis on the
  2-Mass catalog
• From 266 equally-spaced 12 draws from 2Mass
  catalog (with de-redenning, R-I-J-H bands
  photometry analysis)
• Whats missing (faint magnitudes, ratio of K
  dwarfs/giant vs. galactic latitude ) from
  Besancon Galaxy model recipes (Robin et al. 2003)
• - Still ongoing -

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Numbers of transiting planets
Not a lot left
There are still a lot to discover in the 9-12
magnitude range that should be where to push
the effort
Huge numbers, in agreement with the 5 planets
found in OGLE-Carina in just a fraction of square
degree ! (0,342 5 10-6 sky) But are they
worth the FU effort ?
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The case of CoRoT
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Application to CoRoT
Numbers in the CoRoT fields Target
stars F-G-K-M Dwarf stars (from color-mag
diagram) Giant Planets orbiting dwarfs (from RV
surveys) Transiting giant planets (CoRoTlux) Det
ectable giant planets (CoRoTlux using detection
criteria applied by Aigrain, Pont real treatment)

• IRa01
• 9868

• LRc01
• 11408

GIANTS
DWARFS
Mean magnitude of detected events simulated Mean
magnitude of undetected transits
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Application to CoRoT
Numbers in the CoRoT fields Target
stars F-G-K-M Dwarf stars (from color-mag
diagram) Giant Planets orbiting dwarfs (from RV
surveys) Transiting giant planets (CoRoTlux) Det
ectable giant planets (CoRoTlux using detection
criteria applied by Aigrain, Pont real treatment)

• IRa01
• 9868

• LRc01
• 11408

8003 5413
464 81 314 57
6.1 2.0 4.1 1.6
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Application to CoRoT
Numbers in the CoRoT fields Target
stars F-G-K-M Dwarf stars (from color-mag
diagram) Giant Planets orbiting dwarfs (from RV
surveys) Transiting giant planets (CoRoTlux) Det
ectable giant planets (CoRoTlux using detection
criteria applied by Aigrain, Pont real treatment)

• IRa01
• 9868

• LRc01
• 11408

8003 5413
464 81 314 57
6.1 2.0 4.1 1.6
Mean magnitude of detected events simulated Mean
magnitude of undetected transits
4.9 1.7 3.5 1.4
2 Detected planets 2
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Transits detection at the 10-3 level

• Towards a confirmation of the rarity of
  Neptune-size planets ?
• Low expectations in planet formation models
  (Benz 2007)
• More lower mass planets from radial velocity
• More 3-10 Earth masses planets than 10-100 Earth
  masses from gravitational lenses
• Still none discovered by CoRoT

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Transits detection at the 10-3 level
The case of CoRoT Threshold effects
(non-linear decrease of the number of
discoveries vs. Planet size)

• Hypotheses
• Distribution 10 times more small planets than
  giants with a fixed radius in each
  simulation (0.6, 0.4, 0.3, 0.2 Rjup)
• Detection From F.Pont analysis of IRa01 field
  (same results as CoRoT Blind Tests 2 and 3)

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Transits detection at the 10-3 level
The case of CoRoT Threshold effects
(non-linear decrease of the number of
discoveries vs. Planet size)
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The case of M dwarfs

• The Lépine-Shara proper motion (LSPM 2005)
• LSPM also provides known parallaxes and Vmag
  from Tycho-2
• It can be associated with 2Mass catalog for the
  brightest ones to get JHK mags and thus a more
  accurate idea of subtype.
• gt Nutzman-Charbonneau 2007 have identified a list
  of 3300 (very likely) Mdwarfs up to magnitude 16
  in the Northern Hemisphere.
• 1976 are accessible to the MEarth project.
• Mdwarfs are wonderful targets but considering a
  limit to the possibility of the follow-up at Vmag
  17 (Bouchy 2001)
• there are just 15,000 reachable Mdwarfs in all
  sky. And their radii makes transit probability at
  a given period 2 or 3 times more rare than G2
  stars
• i.e. only 7-8 transiting Pegasids in the all sky
  ! (if the distribution is the same than for F-G-K
  dwarfs)
• And probably this order for smaller planets

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What will we get next two years ?
RV photometric follow-up
How successful transit surveys could be consider
now, the most interesting targets all come from
RV surveys ! (Gj436, HD189733, HD209458,
HD149026) We need to be able to catch the
transits of Earths and Super-Earth planets.
KEPLER
KEPLER should be at least an order of magnitude
more precise than any other survey. It should
get accurate light curves of more than 50
Pegasids in the first few weeks/months (72
detections estimated with CoRoTlux) It will
provide Neptune, mini-Neptunes, Super-Earths, but
probably not enough to get a statistically
satisfying sample.
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(Personnal and discussable) Conclusions

• Giant planets
• Most of Pegasid-hosting bright F-G-K stars have
  been found HD189733b could remain the
  brightest exoplanet
• There is still a lot to be found in the Vmag
  9-12 range.
• They may be enough to statistically understand
  Pegasid formation.
• If not, I would stress more on precision than on
  larger numbers
• Neptune-size planets
• - They are less frequent than Pegasids
• - Thus, theres a need for both large numbers
  and precision KEPLER may not be enough to
  provide a statistically sufficient sample !
• M Dwarfs planets
• - Limited numbers of possible discoveries (i.e.
  less than 10 Pegasids in all sky)
• But such interesting targets that its worth the
  risk of failure !

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Optimizing the count of F-G dwarfs
Numbers in the CoRoT fields Target stars F-G
Dwarf stars (catalogs color-color
classification) Giant Planets orbiting
dwarfs (from RV surveys) Transiting giant
planets (CoRoTlux) Detectable giant
planets (CoRoTlux using detection criteria
applied by Aigrain, Pont real treatment)

• LRc02
• 11000

• LRc03
• 11000

4104 10450
252 42 606 112
3.2 1.0 7.9 2.9
2.6 0.9 6.7 2.6
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Introduction
Masse-Rayon des Pégasides
Détection dexoplanètes
Caractérisation dexoplanètes
détection x détection manquée o véritable
planète
CoRoTlux
Principe et Hypothèses
Masse du noyau
Caractéristiques planètes géantes
0-25 MTerre
Accord vitesses radiales
Composition des planètes géantes
Prédictions pour CoRoT
25-50 MTerre
A STEP
Transits au Dôme C
75-100 MTerre
Travaux sur A STEP
50-75 MTerre
Photométrie visible au Dôme C
Perspectives
Fressin et al 2007, 7138-07AA