1. Characterising exoplanetary systems with space-based Bracewell interferometers ARC meeting Denis Defrère Liege, 19 February 2009

2. Motivations Extrasolar planetsExozodiacal discs − Signal: formation, evolution and architecture of planetary systems − Noise: level of exozodiacal dust around nearby MS stars ? Pegase/FKSIExozodiacal discsSuper-EarthConclusions Probing the inner region of planetary systems Observationnal constraints: - high angular resolution - high dynamic (1/10 6 to 1/10 10 )

3. Motivations Pegase/FKSIExozodiacal discsSuper-EarthConclusions 1-zodi disc 300 times brighter than Earth Implications for life-finding nulling interferometry missions:

4. Pegase/FKSIExozodiacal discsSuper-EarthConclusions Pegase/FKSI space-based precursors to Darwin/TPF

5. Mission overview Pegase/FKSIExozodiacal discsSuper-EarthConclusions Pegase - Proposed in 2004 to CNES - Free-flying demonstrator FKSI (Fourier-Kelvin Stellar Interfer.) - GSFC mission (NASA) - Studied at the phase A level

6. Mission overview Instrumental specificationsPeg.FKSI Telescope diameter [m]0.40.5 Wavelength [µm]1.5 – 6.03.0-8.0 Baseline length [m]40-50012.5 Spectral resolution6020 Instrument temperature [K]9065 RMS temp. fluctuations [K]0.1 RMS OPD error [nm]22 RMS pointing error [mas]1520 Pegase/FKSIExozodiacal discsSuper-EarthConclusions

7. Mission overview Pegase/FKSIExozodiacal discsSuper-EarthConclusions Common science objectives: - Spectroscopy of hot extrasolar giant planets - Circumstellar discs - Brown dwarfs - Active galactic nuclei

8. Detection principle Subtracting starlight by destructive interference Pegase/FKSIExozodiacal discsSuper-EarthConclusions

9. Detection principle Exo-planetary system Pegase/FKSIExozodiacal discsSuper-EarthConclusions

10. Exo-planetary system Nulling interferometer Transmission map Detection principle Pegase/FKSIExozodiacal discsSuper-EarthConclusions

11. Exo-planetary system Nulling interferometer Transmission map Detection principle Pegase/FKSIExozodiacal discsSuper-EarthConclusions

12. Exo-planetary system Nulling interferometer Transmission map Local zodiacal cloud Detection principle Pegase/FKSIExozodiacal discsSuper-EarthConclusions

13. Exo-planetary system Nulling interferometer Transmission map Local zodiacal cloud Exozodiacal cloud Detection principle Pegase/FKSIExozodiacal discsSuper-EarthConclusions

14. Pegase/FKSIExozodiacal discsSuper-EarthConclusions Performance for exozodiacal disc detection

15. Adapting the GENIEsim software for space-based nulling interferometers Detectable exozodiacal density for 4 representative Darwin targets FKSI more sensitive in all cases Performance for disc detection. Pegase/FKSIExozodiacal discsSuper-EarthConclusions

16. Comparison with ground-based sites GENIE-UTALADDINPEGASEFKSI Diameter [m]820.40.5 Baseline [m]47-1304-3040-50012.5 Wavelength [µm]3.5-4.13.1-4.11.5-63.0-8.0 SiteCerro ParanalDome CL2 Pegase/FKSIExozodiacal discsSuper-EarthConclusions

17. Comparison with ground-based sites Space-based instruments outperform GENIE and ALADDIN: o Pegase: by a factor 2 to 15; o FKSI: by a factor 25 to 50. Main advantages: o Low thermal background; o Good OPD control. Pegase/FKSIExozodiacal discsSuper-EarthConclusions

18. Prospects for Super-Earth detection Pegase/FKSIExozodiacal discsSuper-EarthConclusions

19. “Super-Earth” extrasolar planets 1. Main characteristics: − Between 2 and 10 Earth masses − 14 detected so far by radial velocity, microlensing or pulsar timing: around low-mass stars semi-major axes range between 0.02 and 2 au − Found likely in multiplanetary systems (80% known candidates) 2. Favorable examples: HD40307bHD40307cHD40307dHD285968b Planet mass [M  ]4.26.99.28.4 Planet s-major axis [au]0.0470.0810.1340.066 Stellar spectral typeK2.5V M2.5V Stellar distance [pc]13 9.4 ReferenceMayor et al. 2009 Forveille et al. 2008 Pegase/FKSIExozodiacal discsSuper-EarthConclusions

20. Detection of know Super-Earths Pegase/FKSIExozodiacal discsSuper-EarthConclusions FKSI not well suited for known Super-Earths (baseline too short)

21. Detection of know Super-Earths Pegase/FKSIExozodiacal discsSuper-EarthConclusions HD40307bHD40307cHD40307dHD285968b Planet mass [M  ]4.26.99.28.4 Planet s-major axis [au]0.0470.0810.1340.066 Angular separation [mas]3.66.210.37.1 FKSI transmission (8 µm)>0.010.020.060.03 FKSI modulation efficiency>0.010.020.030.01

22. Detection sensitivity Pegase/FKSIExozodiacal discsSuper-EarthConclusions FKSI not convenient for Super-Earths Could detect Neptune-sized planets (SNR increases as R p ²)

23. GENIE: 80% ALADDIN: 35% PEGASE: 50% FKSI: 30% 1354 target star in the Darwin/TPF catalogue ALADDIN and space-based instruments complementary Sky coverage Pegase/FKSIExozodiacal discsSuper-EarthConclusions

24. Pegase/FKSIExozodiacal discsSuper-EarthConclusions Summary and conclusions Performance study for exozodiacal disc detection −Space-based instruments far more sensitive −Detection achieve very quickly −FKSI: 1-zodi level achievable for all Darwin/TPF targets −Pegase: shorter baseline configuration highly recommended Prospects for Super-Earth exoplanet detection −FKSI not convenient to observe Super-Earth exoplanets −Can do the job for some short period Super-Earths Sky coverage complementary with ALADDIN

25. Nulling interferometryPegaseDarwinConclusions Motivations Most detections by indirect techniques − Planetary photons not collected − Limited information on planets Direct detection difficult – High star/planet contrast (10 7 -IR and 10 10 -visible) – Small angular separation (0.1" for an Earth-Sun system located at 10pc) 5×10 9 7×10 6

26. Nulling interferometryPegaseDarwinConclusions Comparison with ground-based sites

27. Nulling interferometryPegaseDarwinConclusions Principles Subtracting starlight by destructive interference Transmission map b