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Reflected Light From Extra 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. Introduction. 119 extra solar planets detected.
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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
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).
Reflected light • Amount of reflected light given by: p=albedo d=planet-star separation =phase function Rp=planet radius
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
Elliptical Orbits Apocentre Pericentre Semi-major axis
Eccentricities of Extra Solar Planets Eccentricity Semi-major axis (AU)
Orientation of the orbital plane - Inclination Inclination: i=0° (face on)
Orientation of the orbital plane - Argument of Pericentre To observer Argument of pericentre: ω=0°
To observer Argument of pericentre: ω=90°
To observer Argument of pericentre: ω=-90°
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
Example Light Curve 8 x 10-6 i=90o (Edge on) LP / L* 0 P days Pericentre Apocentre Time
8 x 10-6 i=75o LP / L* 0 P days Time
8 x 10-6 i=60o LP / L* 0 P days Time
8 x 10-6 i=45o LP / L* 0 P days Time
8 x 10-6 i=30o LP / L* 0 P days Time
8 x 10-6 i=15o LP / L* 0 P days Time
8 x 10-6 i=0o (Face on) LP / L* 0 P days Time
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 = ?
HD 108147b 40 x 10-6 LP / L* 0 10.9 days Time
Contrast 10 x 10-6 contrast LP / L* 0 10.9 days Time
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)
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)
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)
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.