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Characterising exoplanetary systems with space-based Bracewell interferometers

This study explores the role of space-based Bracewell interferometers, such as Pegase and FKSI, in characterizing exoplanetary systems. Key motivations include probing inner regions of planetary systems and gaining insights into exozodiacal dust and signal noise levels around nearby stars. The paper highlights the instruments' unique capabilities in high angular resolution and dynamic range performance, outperforming ground-based systems. Furthermore, it discusses prospects for detecting Super-Earths and the potential for life-finding missions, ultimately aiming to advance our knowledge of planetary formation and evolution.

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Characterising exoplanetary systems with space-based Bracewell interferometers

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

  2. Motivations • Probing the innerregion of planetarysystems • Observationnalconstraints: • - highangularresolution • - highdynamic (1/106 to 1/1010) ? Exozodiacal discs Extrasolarplanets • Signal: formation, evolution and architecture of planetarysystems • Noise: level of exozodiacaldustaroundnearby MS stars

  3. Motivations • 1-zodi disc 300 times brighterthanEarth • Implications for life-findingnullinginterferometry missions:

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

  5. Mission overview • Pegase • Proposed in 2004 to CNES • Free-flyingdemonstrator • FKSI (Fourier-Kelvin StellarInterfer.) • GSFC mission (NASA) • Studiedat the phase A level

  6. Mission overview

  7. Mission overview • Common science objectives: • Spectroscopy of hot extrasolargiantplanets • Circumstellar discs • Brown dwarfs • Active galacticnuclei

  8. Detection principle Subtracting starlight by destructive interference

  9. Performance for exozodiacal disc detection

  10. Performance for disc detection . • Adapting the GENIEsim software for space-based nulling interferometers • Detectable exozodiacal density for 4 representative Darwin targets • FKSI more sensitive in all cases

  11. Comparison with ground-based sites

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

  13. Prospects for Super-Earth detection

  14. “Super-Earth” extrasolar planets • 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 • Foundlikely in multiplanetarysystems (80% known candidates) • Favorable examples:

  15. Detection of know Super-Earths • FKSI not well suited for known Super-Earths (baseline too short)

  16. Detection of know Super-Earths

  17. Detection sensitivity • FKSI not convenient for Super-Earths • Could detect Neptune-sized planets (SNR increases as Rp²)

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

  19. 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

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