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Reflected Light From Extra Solar Planets

Study exploring modeling of reflected light from extra-solar planets with highly elliptical orbits, using Kepler and MOST data. Analyzing light curves, orientation, and contrast to understand planetary properties.

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Reflected Light From Extra Solar Planets

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  1. Reflected Light FromExtra Solar Planets Modeling light curves of planets with highly elliptical orbits Daniel Bayliss, Summer Student, RSAA, ANU Ulyana Dyudina, RSAA, ANU Penny Sackett, RSAA, ANU

  2. Introduction • 119 extra solar planets detected. • 118 found by precise radial velocity measurements. • 1 by found by transit photometry. • No reflected light from extra solar planets detected to date, however the albedo of τ Boo constrained by lack of signal (Charbonneau et al.,1999, ApJ, 522, L145).

  3. Reflected light • Amount of reflected light given by: p=albedo d=planet-star separation =phase function Rp=planet radius

  4. Space Photometry • Current photometric precision limited by atmosphere to around LP/L* ~50 x 10-6. • Canadian micro satellite MOST target list includes 3 stars with planets (close-in, circular). • NASA’s Kepler satellite (2007) with 100,000+ target stars. • Predicted to achieve precision of LP/L*< 10 x 10-6. Kepler MOST

  5. Elliptical Orbits Apocentre Pericentre Semi-major axis

  6. Eccentricities of Extra Solar Planets Eccentricity Semi-major axis (AU)

  7. Orientation of the orbital plane - Inclination Inclination: i=0° (face on)

  8. Inclination: i=10°

  9. Inclination: i=45°

  10. Inclination: i~90° (edge on)

  11. Orientation of the orbital plane - Argument of Pericentre To observer Argument of pericentre: ω=0°

  12. To observer Argument of pericentre: ω=90°

  13. To observer Argument of pericentre: ω=-90°

  14. Model • Reflective properties of planets based on Pioneer data of Jupiter. • Planetary radius assumed to be 1 Jupiter radius. • Example light curve properties: • Semi-major axis = 0.1 AU • Argument of pericentre = 60° • Eccentricity = 0.5

  15. Example Light Curve 8 x 10-6 i=90o (Edge on) LP / L* 0 P days Pericentre Apocentre Time

  16. 8 x 10-6 i=75o LP / L* 0 P days Time

  17. 8 x 10-6 i=60o LP / L* 0 P days Time

  18. 8 x 10-6 i=45o LP / L* 0 P days Time

  19. 8 x 10-6 i=30o LP / L* 0 P days Time

  20. 8 x 10-6 i=15o LP / L* 0 P days Time

  21. 8 x 10-6 i=0o (Face on) LP / L* 0 P days Time

  22. Example - HD 108147b • Extra solar planet discovered by Pepe, Mayor, et al (2002, A&A , 388, 632). • Properties: • Semi-major axis = 0.104 AU • Period = 10.9 days • Eccentricity = 0.498 • Argument of pericentre = -41° • Inclination = ?

  23. HD 108147b 40 x 10-6 LP / L* 0 10.9 days Time

  24. Contrast 10 x 10-6 contrast LP / L* 0 10.9 days Time

  25. Contrastfor e=0 Scale at 0.1 AU (x10-6) 90 100 10 1 0.1 Kepler Inclination (i) 0 90 0 -90 Argument of pericentre (ω)

  26. Contrastfor e=0.6 Scale at 0.1 AU (x10-6) 90 100 10 1 0.1 Inclination (i) 0 90 0 -90 Argument of pericentre (ω)

  27. Contrastfor various e Scale at 0.1 AU (x10-6) 100 10 1 0.1 e=0 e=0.1 e=0.2 Inclination (i) e=0.3 e=0.4 e=0.5 e=0.6 e=0.7 e=0.8 Argument of pericentre (ω)

  28. Conclusions • A low inclination (face on) orientation can show strong contrast if it has a high eccentricity orbit. • Light curves from elliptical orbits may help constrain a systems inclination. • Favourable pericentric orientation can dramatically increase the contrast.

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