Reflected Light From Extra Solar Planets

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.