IAP Fressin

Slide1: 

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, 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 STEP Antarctica Search for Transiting Extrasolar Planets

The future of transit searches: 

The future of transit searches Combined to radial-velocimetry, it is the only way to determine the density, hence the global composition of a planet 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 searches: 

The future of transit searches 2 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 Earth A 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 Determine the limits of Dome C for precise wide field photometry (Scintillation and photon noise … or other noise sources ?) 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) Search for transiting exo-planets and characterization of these planets – Detection of bright stars oscillations.

A STEP: the philosophy behind: 

A 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 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 STARE OGLE HATnet Vulcan UNSW Number of detections expected per season 14 17.2 11 11 13.6 Simulation considering « systematic effects » 0.9 1.1 0.2 0.6 0.01 Real number of detections 1 1.2 0 0 0 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 (F.Pont 2005) : 

Systematic effects (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

Slide10: 

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 observations

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

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

Observing at dome C – Lessons from first two 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 dilatations inside the telescope

Slide13: 

THE A STEP TEAM

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A STEP Telescope CCD DW 436 (Andor) Size 2048 x 2048 Pixel size 13.5 mm 1.74 arcsec on sky A STEP Characteristics: Camera use: Defocused PSF PSF sampling: FWHM covering ~4 pixel Time exposure: 10s Readout time: 10s Telescope mount: German Equatorial Astrophysics 1200 With controlled heating Pointing precision tolerated ~.5” Contractor: Optique et Vision ERI

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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

Slide16: 

A precise photometric telescope at Dome C Telescope tube: INVAR structure With Carbon fiber coverage Thermal enclosure for focal instrumentation Wynne Corrector 4Mpixel DW436 CCD

Slide17: 

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

Slide18: 

Target stellar field for first campaign

Slide19: 

Data processing Re-use of the major part of BEST (Berlin Exoplanet Search Telescope) data pipeline (Erikson, Rauer)

Slide20: 

Schedule of A STEP

Slide21: 

Schedule of A STEP

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CoRoTlux Stellar field generation with astrophysical noise sources Light curves generation and 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, … Exemples of results of two CoRoTlux simulations

Slide24: 

False Transit Discrimination

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Many events mimic transits … ! background eclipsing binaries background planets target planets target binaries Number of events for 1 CoRoT CCD CoRoTlux (Guillot et al.) Grazing Eclipsing Binaries M Dwarfs Triple Systems

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Blends discrimination Within 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 with high 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 … ?

Slide28: 

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

Slide29: 

Global ongoing study: Simulation of the optimal transit search program

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