Detection of Ks-band Thermal Emission from WASP-3b

TL;DR

This study reports the successful detection of thermal emission from exoplanet WASP-3b in the Ks band, demonstrating improved observational techniques and providing insights into its atmospheric properties and orbital eccentricity.

Contribution

Developed a new guiding scheme for WIRC that enhanced photometric precision, enabling the first Ks-band thermal emission detection from WASP-3b and analysis of its atmospheric and orbital characteristics.

Findings

Detected 0.181% secondary eclipse depth with 9-sigma significance.

Results favor a radiative equilibrium atmosphere with no heat redistribution.

Orbit is consistent with being circular, with possible slight eccentricity.

Abstract

We report the detection of thermal emission from the hot Jupiter WASP-3b in the KS band, using a newly developed guiding scheme for the WIRC instrument at the Palomar Hale 200in telescope. Our new guiding scheme has improved the telescope guiding precision by a factor of ~5-7, significantly reducing the correlated systematics in the measured light curves. This results in the detection of a secondary eclipse with depth of 0.181%\pm0.020% (9-{\sigma}) - a significant improvement in WIRC's photometric precision and a demonstration of the capability of Palomar/WIRC to produce high quality measurements of exoplanetary atmospheres. Our measured eclipse depth cannot be explained by model atmospheres with heat redistribution but favor a pure radiative equilibrium case with no redistribution across the surface of the planet. Our measurement also gives an eclipse phase center of 0.5045\pm0.0020, corresponding to an ecos{\omega} of 0.0070\pm0.0032. This result is consistent with a circular orbit, although it also suggests the planet's orbit might be slightly eccentric. The possible non-zero eccentricity provides insight into the tidal circularization process of the star-planet system, but also might have been caused by a second low-mass planet in the system, as suggested by a previous transit timing variation study. More secondary eclipse observations, especially at multiple wavelengths, are necessary to determine the temperature-pressure profile of the planetary atmosphere and shed light on its orbital eccentricity.