Jeffrey L. Coughlin, Mercedes Lopez-Morales
We present the results of searching the Kepler Q2 public dataset for the
secondary eclipses of 76 hot Jupiter planet candidates from the list of 1,235
candidates published by Borucki et al. (2011). This search has been performed
by modeling both the Kepler PDC light curves and new light curves produced via
our own photometric pipeline. We derive new stellar and planetary parameters
for each system with robust errors. We find 16 systems with 1-2 sigma, 14
systems with 2-3 sigma, and 6 systems with >3 sigma confidence level secondary
eclipse detections in at least one light curve. We find that the majority of
detected planet candidates emit more light than expected due to thermal
blackbody emission in the optical Kepler bandpass, and present a trend of
increasing excess emission with decreasing maximum effective planetary
temperature. We explore modeling biases, significant planetary albedos, non-LTE
or other thermal emission, significant internal energy generation, and
exoplanet mis-identification as possible causes of both the excess emission and
its correlation with expected planetary temperature. Although we find no single
cause is able to explain all of the planet candidates, significant planetary
albedos, with a general trend of increasing planetary albedos with decreasing
atmospheric temperatures, is able to explain most of the systems. We estimate
an 11% false positive rate in the current Kepler planet candidate sample of hot
Jupiters. We also establish robust upper limits on the eclipse depth for all
systems, and find that a significant fraction of these systems have very low
albedos, significantly augmenting and extending the sample of albedo
determinations to planets as cool as 1200 K. Finally, we note that continued
observations with Kepler, and improved techniques for the removal of systematic
noise in the Kepler data, are needed to better characterize these systems.
View original:
http://arxiv.org/abs/1112.1021
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