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. – 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=albedod=planet-star separation  =phase function R p =planet radius

Space Photometry Current photometric precision limited by atmosphere to around L P /L * ~50 x 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 L P /L * < 10 x MOST Kepler

Elliptical Orbits Semi-major axis ApocentrePericentre

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

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

Inclination: i=10°

Inclination: i=45°

Inclination: i~90° (edge on)

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

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

Time P days 8 x Example Light Curve i=90 o (Edge on) L P / L * PericentreApocentre

Time 8 x i=75 o 0 L P / L * P days

Time 8 x i=60 o 0 L P / L * P days

Time 8 x i=45 o 0 L P / L * P days

Time 8 x i=30 o 0 L P / L * P days

Time 8 x i=15 o 0 L P / L * P days

Time 8 x i=0 o (Face on) 0 L P / L * P days

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

Time 10.9 days 40 x HD b 0 L P / L *

Time 10.9 days 10 x Contrast contrast 0 L P / L *

Contrast for e=0 Inclination (i) Scale at 0.1 AU (x10 -6 ) Argument of pericentre (ω) 090 Kepler

Contrast for e=0.6 Inclination (i) Scale at 0.1 AU (x10 -6 ) Argument of pericentre (ω)

Contrast for various e Argument of pericentre (ω) Scale at 0.1 AU (x10 -6 ) Inclination (i) e=0.6 e=0.7 e=0.8 e=0 e=0.1 e=0.2 e=0.3 e=0.4 e=

Conclusions 1.A low inclination (face on) orientation can show strong contrast if it has a high eccentricity orbit. 2.Light curves from elliptical orbits may help constrain a systems inclination. 3.Favourable pericentric orientation can dramatically increase the contrast.