Phase Functions and Light Curves of Wide Separation Extrasolar Giant Planets

Astrophysics, abstract
astro-ph/0501109

From: David Sudarsky [view email]

Date: Thu, 6 Jan 2005 22:09:33 GMT   (202kb)

We calculate self-consistent extrasolar giant planet (EGP) phase functions
and light curves for orbital distances ranging from 0.2 AU to 15 AU. We explore
the dependence on wavelength, cloud condensation, and Keplerian orbital
elements. We find that the light curves of EGPs depend strongly on wavelength,
the presence of clouds, and cloud particle sizes. Furthermore, the optical and
infrared colors of most EGPs are phase-dependent, tending to be reddest at
crescent phases in $V-R$ and $R-I$. Assuming circular orbits, we find that at
optical wavelengths most EGPs are 3 to 4 times brighter near full phase than
near greatest elongation for highly-inclined (i.e., close to edge-on) orbits.
Furthermore, we show that the planet/star flux ratios depend strongly on the
Keplerian elements of the orbit, particularly inclination and eccentricity.
Given a sufficiently eccentric orbit, an EGP’s atmosphere may make periodic
transitions from cloudy to cloud-free, an effect that may be reflected in the
shape and magnitude of the planet’s light curve. Such elliptical orbits also
introduce an offset between the time of the planet’s light curve maximum and
the time of full planetary phase, and for some sets of orbital parameters, this
light curve maximum can be a steeply increasing function of eccentricity. We
investigate the detectability of EGPs by proposed space-based direct-imaging
instruments.

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