F.Fressin, T.Guillot Y.Rabbia, A.Blazit, JP. Rivet, J.Gay, D.Albanese, V.Morello, N.Crouzer (OCA - Nice), F.X Schmider, K.Agabi, J-B. Daban, E.Fossat,

F.Fressin, T.GuillotY.Rabbia, A.Blazit, JP. Rivet, J.Gay, D.Albanese, V.Morello, N.Crouzer (OCA - Nice),

F.X Schmider, K.Agabi, J-B. Daban, E.Fossat, L.Abe, C.Combier,F.Janneaux,Y. Fantei (LUAN – Nice)

C.Moutou, F.Bouchy, M.Deleuil, M.Ferrari, A.Llebaria, M.Boer, H.Le Corroler, A.Klotz,A.Le van Suu,J. Eysseric, C Carol (OAMP - Marseille),

A.Erikson, H.Rauer (DLR - Berlin),

F.Pont (Obs. Genève)

A STEPA STEP Antarctica Search for Transiting Antarctica Search for Transiting

Extrasolar PlanetsExtrasolar Planets

The future of transit searchesThe future of transit searches

Combined to radial-velocimetry, it is the only way to determine the density, hence the global composition of a planet

Transit spectroscopy offers additional possibilities not accessible for “normal” planets

examples:A correlation between the metallicity of stars and planets (Guillot et al. A&A 2006)

Planetary formation model constraints (Sato et al 2005)

We foresee that exoplanetology will have as its core the study of transiting exoplanets

The future of transit searchesThe future of transit searches2 future milestones:•COROT: 60 000 stars (nominal mission), mv=11 to 16, for 150 days, launch oct. 2006•KEPLER: 100 000 stars, mv=11 to 14 for 4 years, + 70 000 for 1 year, launch end 2008

Limited by data transmission to EarthA problem for the detection of small planets: background eclipsing binaries

Future missions should:•Detect more planets•Diversify the targets•Detect smaller planets

from SPACE•Natural but costly•Limited in telescope size, number of instruments...

from DOME C•Promising but uncertain•Requires precursor mission(s)

Why transit searches at Dome C?Why transit searches at Dome C?

•Continuous night for 3 months•Excellent weather

Questions:We don’t know how the following factors will affect transit surveys:

•Sky brightness & fluctuations•Presence of the moon•Generally, systematics effect due to the combination of astrophysical, atmospheric and instrumental noises

Technical problems•Autonomous operations in cold (-50°C to -80°C) conditions•Temperature fluctuations•Icing•Electrical discharges

A STEP Objectives A STEP Objectives

1. Determine the limits of Dome C for precise wide field photometry (Scintillation and photon noise … or other noise sources ?)

2. If the site is competitive with space and transit search limits are well understood, establish the bases of a mid-term massive detection project (large Schmidt telescope or network of small ones)

3. Search for transiting exo-planets and characterization of these planets – Detection of bright stars oscillations.

A STEP: the philosophy behindA STEP: the philosophy behind

•Prepare future photometric projects for planetary transit detection at Dome C

•Use available equipment, minimize development work for a fast implementation of the project

•Use experience acquired from the site testing experiment Concordiastro

•Semi-automated operation

•Directly compare survey efficiency at Dome C with BEST 2 in Chile for the same target field

Ground based transit projects Ground based transit projects Program Observing site Status Telescope Instrument

FieldofView

Limitingmagnitude

Stars/FOV Precision

VulcanMt. Hamilton,California

observing 5,4 cm

SpectralInstruments-560,KodakKAF16800 4k x4k CCD, CanonEF300 F/2.8

7 x7

13 mag 6000 1%

Hat-1 Kitt Peak, Arizonaunderconstruction

6,4 cm

Apogee AP 10,ThomsonTHX7899M 2k x2k, Nikon180mm f/2.8 MF

9 x9

13 mag 20000 0,01 mag

ASAS-3 Ź observing 7,1 cmApogee AP 102k x 2k, Minolta200/2.8

8,8x8,8

14 mag 8000 Ź

STARETenerife, CanaryIslands

observing 10 cmPixelvision 2k x2k CCD, f/2.9

Ź 25000 Ź

BESTThueringerLandessternwarte,Germany

observing 20 cm

CCD AP10Apogee,ThomsonTHX899M

3.1x3.1

13 mag 30000 < 1%

WASP0 Ź Project 10 inch

F/2.8 Nikon,Apogee 10 CCDcamera(2k x 2k)

9 x9

14 mag Ź 1 %

SuperWASPLa Palma, CanaryIslands

underconstruction

11,1 cm

Canon 200mmf/1.8, 2k x 2kthinned EEVproduced byAndor of Belfast

9.5x9.5

13 mag 43000 Ź

APTSiding SpringObservatory,Australia

observing 80 cm Ź2 x3

13 mag Ź 1%

OGLELas CampanasObservatory,Chile

observing 130 cm

8kMOSAIC CCDcamera (SITe2048 x 2049 thinchip )

35' x35'

Ź Ź Ź

STELLATenerife, CanaryIslands

underconstruction

???CCD42-40ŹNIMO2k x 2k

Ź Ź Ź Ź

RAPTOR AFenton Hill,Jemez Mountains

underconstruction

70 cm

Apogee AP10,Thomson 7899MCCD 2k x 2k,Canon 85mmf/1.2

19,5x19,5

12 mag Ź Ź

10 transiting planets discovered up to date– 4 radial velocities +

photometric follow up

– 5 OGLE– 1 STARE/TrES

Transits photometry – Any problem ? Transits photometry – Any problem ?

A huge difference between the expected number of detections and reality :

Project

STAREOGLEHATnetVulcanUNSW

Number of detections

expected per season

1417.21111

13.6

Simulation considering

« systematic effects »

0.91.10.20.6

0.01

Real number of detections

11.2000

Red Noise

These red noises, or «systematic effects » are all the noises undergoing temporal correlations and that we can not subtract easily.

DUTY CYCLE

These numbers really depend of the duty cycle of each campaign

Systematic effects Systematic effects (F.Pont 2005)(F.Pont 2005)

•We only have a partial knowledge of these effects

•They seem to all result from interaction between environmental effects with instrumental characteristics (Pont 2005)

•They are closely linked to the spatial sampling quality

•For OGLE, the principal source is differential refraction linked to air mass changes. (Zucker 2005)

— magnitude dependence with white noise

— magnitude dependence with red noise

A good phase coverage is determinant to detect the large majority of transits from ground

OGLE: transits discovered•really short periods P ~ 1 day (rare !)•stroboscopic periods

Hot Jupiters: periods around 3 days, depth ~1%

Probability of detection of a transit for a survey of 60 days

With OGLE

For the same telescope with a permanent phase coverage

Continuous observationsWith a “classical” survey, only the “stroboscopic” planets are detectable !

Observing at dome C – Lessons from Observing at dome C – Lessons from first two winter campaigns (1)first two winter campaigns (1)

Confirmation by the first winter campaign of the exceptional phase coverage (cloud coverage, austral auroras)

Environmental systematic effects considerably reduced:• air mass• timescale of environmental parameters evolution

Expectations for future transits search programs• low scintillation

« First Whole atmosphere night seeing measurements at Dome C, Antarctica » Agabi, Aristidi, Azouit, Fossat, Martin, Sadibekova, Vernin, Ziad

An exceptional coverage …

Observing at dome C – Lessons from first two Observing at dome C – Lessons from first two winter campaigns (2)winter campaigns (2)

… But a lot of technical difficulties to take into account

Frost – different Behaviour for different telescopes

Telescope mounts missfunctionning at really low temperature

Differential dilatationsinside the telescope

Observatoire de la Côte d'Azur (Laboratoires Cassiopée et Gemini):

Tristan Guillot (PI)                        

Scientific preparation, operation supervision, preparation of modelling tools, analysis of the results and scientific interpretation

Francois Fressin (IS)Scientific and technical preparation, modelling tools, analysis of the results and scientific interpretation

Alain BlazitResponsible of the camera team; Developpement of test and acquisition tools.

Jean GayFollow-up of the telescope conception; Technical preparation, optical properties modelling

Yves Rabbia Telescope environment, follow-up of the telescope conception

Jean-Pierre Rivet Telescope environment, flat fielding system

Dominique Albanese Camera control softwares & camera testing expertise

Laboratoire Universitaire d'Astrophysique de Nice:

François-Xavier SchmiderScientific and technical preparation (telescope), Dome C logistics, analysis of the results and scientific interpretation

Karim Agabi (PM)Technical preparation, Dome C logistics, telescope design and telescope control systems

Jean-Batiste DabanTechnical preparation, Dome C logistics, telescope design and telescope control systems

Eric FossatDome C logistics, analysis of the results and scientific interpretation

Lyu Abe Quality control, tests and installation

Cécile Combier Telescope and camera control softwares

François Jeanneaux Mechanical study of the camera environment

Yan Fantei Temperature regulation system, camera control system

Observatoire Astrophysique de Marseille Provence (LAM & OHP):

Claire MoutouScientific preparation, follow-up of transit candidates, photometric reduction

Magali Deleuil Scientific preparation, follow-up of transit candidates

Marc FerrariConsulting on optical properties of the telescopes, tests and optical simulations

François Bouchy Scientific preparation, follow-up of transit candidates

Antoine Llebaria Image processing, stellar photometry

Michel BoerResponsible for providing a telescope control system based on TAROT, scientific interpretation

Hervé Le Corroler Scientific interpretation

Alain Klotz Telescope and camera control software, scientific interpretation

Auguste Le van Suu Computer interfaces, telescope control system

Jérome Eysseric System engineer

Claudine Carol Computer engineer

Observatoire de Genève:

Frédéric PontScientific preparation, specifications, analysis of the results, follow-up of transit candidates, scientific interpretation

Deutsches zentrum für Luft und Raumfart:

Anders EriksonAdaptation of the data reduction pipeline; Experience with running the transit surveys BEST (OHP) and BEST II (La Silla)

Heike RauerScientific preparation, specifications, analysis of the results, comparison of BEST II / A STEP data

THEA STEP TEAM

A STEP Telescope

CCD DW 436 (Andor)Size 2048 x 2048Pixel size 13.5 m1.74 arcsec on sky

A STEP Characteristics:

Camera use:Defocused PSFPSF sampling: FWHM covering ~4 pixelTime exposure: 10sReadout time: 10s

Telescope mount:German Equatorial Astrophysics 1200With controlled heatingPointing precision tolerated ~.5”

Contractor:Optique et VisionERI

A STEP Camera : Andor DW436

-2048x2048 pixel-Backwards illuminated CCD-Limited intra-pixel fluctuations (Karoff 2001)-Excellent quantum efficiency in red-USB2 with antarctisable connection

A precise photometric telescope at Dome C

Telescope tube:INVAR structure With Carbon fiber coverage

Thermal enclosure for focal instrumentation

Wynne Corrector4Mpixel DW436 CCD

Mode of operation

• One field followed continuously (first year) • Flatfields from illuminated white screens• Data storage: ~500 GB /campaign• Data retrieval at the beginning of Antarctic Summer• Redundancy:

-Two computers in an “igloo” next to the telescope-Two miror PCs in the Concordia Command Center (fiber link)-Two backup PCs

•Semi-automatical: -Simple control and maintenance every 48 hours

Target stellar field for first campaign

Data processingRe-use of the major part of BEST

(Berlin Exoplanet Search Telescope) data pipeline (Erikson, Rauer)

Schedule of A STEP

•PNP, CSA: 64 k€ (approved)•ANR: 208 k€ (pending)

Schedule of A STEP

CoRoTluxStellar field generation

with astrophysical noise sources

Light curves generationand transit search algorithms

coupling

Blends simulation

Expected results … Expected results …

Considering only planets Giant Planets (Hot Saturn and Jupiter)

Simulation done with CoRoTlux considering 4 stellar fields (1 first year, 3 second year)

Average of 12 Giant Planets for 10 Monte-Carlo draws

Using CoRoTlux simulator (end to end stellar field to light curves generator)Guillot, Fressin, Pont, Marmier, …

11 12 13 14 15 16 17

Stellar Magnitude

Tra

nsit

Dep

thT

rans

it D

epth

Exemples of results of two CoRoTlux simulations

False TransitDiscrimination

Many events mimic transits … !

backgroundeclipsing binaries

backgroundplanets

targetplanets

targetbinaries

Number of events for 1 CoRoT CCD CoRoTlux (Guillot et al.)

Grazing Eclipsing Binaries

M Dwarfs

Triple Systems

Blends discriminationWithin lightcurve:

+Secondary transits+Detection level+Exoplanet “diagnostic” or “minimal radius” Tingley & Sackett+Ellipsoidal variability of close binaries (Sirko & Paczynski 2003)+ Photocenter of the fluctuation

Ground based follow-up:

+Radial velocities (provides confirmation by a different method AND planet characterization) – HARPS

+Precise photometry withhigh resolution telescopes and Adaptive optics for critical cases

-> 70 to 90 % of transit candidates could be discriminated within lighturves(Estimation from CoRoTlux results – Fressin)

->99+ % false events discrimination goal-> confirmation of most transits with radial velocities … ?

Conclusions• A STEP

– Is supported by 6 laboratories, French Dome C commission, Exoplanet group, Planetology National Program

– Would allow to detect in one season as many transits as all other ground based transit programs in several years.

– Will do the photometric test of Dome C for future transit search programs …

Transit research is determinant for exoplanet characterization

– Planetary formation and solar system models

– A cornerstone for exobiology programs

• CoRoT- Will discover and characterize most of the short period giant planets in its fields, thus largely increase our knowledge of exoplanets

- Will provide statistical information on the presence of short periods smaller planets - Could provide the first characterization of super-earth planets

Global ongoing study: Simulation of the optimal transit search

programCOROTLUX->Stellar Field generator – Guillot et al(astrophysical noise sources)

Point Spread Function and image on CCD – (Fressin, Gay) (instrumental and atmospheric noises – masks/PSF fitting)Light curves

generator-> Systematic and environmental effects

Search of transits in lightcurves-> Treatment, transit search, discrimination(-> Number of detections)

Why searching for transits?Why searching for transits?

Only possible way known to measure an exoplanet radius

Combined with radial velocity measurements: Mass, density,

composition

Capacity to detect small objets Jupiter: 1%; Earth:

0.01%

Radius measurement(photometry)

Mass Measurement(radial velocities)

Ground based projects were almost unable to discover objects like Hot Jupiter up today –

But there will be great returns as

their detection threshold increases