Detection of KS -band Thermal Emission from WASP-3b
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 200 inch 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% ± 0.020% (9σ)—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 favors 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 ± 0.0020, corresponding to an ecos ω of 0.0070 ± 0.0032. This result is consistent with a circular orbit, although it also suggests that 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 might also 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 planet's atmosphere and shed light on its orbital eccentricity.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2012
- DOI:
- 10.1088/2041-8205/748/1/L8
- arXiv:
- arXiv:1202.3435
- Bibcode:
- 2012ApJ...748L...8Z
- Keywords:
-
- infrared: planetary systems;
- planetary systems;
- stars: individual: WASP-3;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 14 pages, including 4 figures. Accepted for publication in ApJ Letters