View
218
Download
0
Tags:
Embed Size (px)
Citation preview
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.
MOST
Kepler
Elliptical Orbits
Semi-major axis
Apocentre Pericentre
Eccentricities of Extra Solar PlanetsE
ccen
tric
ity
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
TimeP days
8 x 10-6
0
Example Light Curve
i=90o (Edge on)
LP
/ L
*
Pericentre Apocentre
Time
8 x 10-6
i=75o
0
LP
/ L
*
P days
Time
8 x 10-6
i=60o
0
LP
/ L
*
P days
Time
8 x 10-6
i=45o
0
LP
/ L
*
P days
Time
8 x 10-6
i=30o
0
LP
/ L
*
P days
Time
8 x 10-6
i=15o
0
LP
/ L
*
P days
Time
8 x 10-6
i=0o (Face on)
0
LP
/ L
*
P days
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 = ?
Time10.9 days
40 x 10-6
HD 108147b
0
LP
/ L
*
Time10.9 days
10 x 10-6
Contrast
contrast
0
LP
/ L
*
Contrast for e=0In
clin
atio
n (i
)
90
0-90
Scale at 0.1 AU (x10-6)
100
10
1
0.1
Argument of pericentre (ω)
090
Kepler
Contrast for e=0.6In
clin
atio
n (i
)
90
0-90
Scale at 0.1 AU (x10-6)
Argument of pericentre (ω)
090
100
10
1
0.1
Contrast for various e
Argument of pericentre (ω)
Scale at 0.1 AU (x10-6)
Incl
inat
ion
(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=0.5
100
10
1
0.1
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.