Can We Probe the Atmospheric Composition of an Extrasolar Planet from its Reflection Spectrum in a High-Magnification Microlensing Event?

Astrophysics, abstract
astro-ph/0501107

From: David Spiegel [view email]

Date: Fri, 7 Jan 2005 03:10:48 GMT   (179kb)

We revisit the possibility of detecting an extrasolar planet around a
background star as it crosses the fold caustic of a foreground binary lens.
During such an event, the planet’s flux can be magnified by a factor of
approximately 100 or more. We find that the detectability of the planet depends
strongly on the orientation of its orbit relative to the caustic. If the source
star is inside the inter-caustic region, detecting the caustic-crossing planet
is difficult against the magnified flux of its parent star. In the more
favorable configuration, when the star is outside the inter-caustic region when
the planet crosses the caustic, we find that a close-in Jupiter-like planet
around a Sun-like star at a distance of 8 kpc is detectable in 8-minute
integrations with a 10m telescope at approximately S/N=15. In this example, we
find further that the presence of methane, at its measured abundance in
Jupiter, and/or water, sodium and potassium, at the abundances expected in
theoretical atmosphere models of close-in Jupiters, could be inferred from a
non-detection of the planet in strong broad absorption bands at 0.6-1.4 microns
caused by these compounds, accompanied by an approximate S/N=10 detection in
adjacent bands. We conclude that future generations of large telescopes might
be able to probe the composition of the atmospheres of distant extrasolar
planets.

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