paper

3.6 and 4.5 m Phase Curves of the Highly-Irradiated Hot Jupiters WASP-19b and HAT-P-7b

arXiv:1512.09342 · doi:10.3847/0004-637X/823/2/122

Abstract

We analyze full-orbit phase curve observations of the transiting hot Jupiters WASP-19b and HAT-P-7b at 3.6 and 4.5 m obtained using the Spitzer Space Telescope. For WASP-19b, we measure secondary eclipse depths of and at 3.6 and 4.5 m, which are consistent with a single blackbody with effective temperature K. The measured 3.6 and 4.5 m secondary eclipse depths for HAT-P-7b are and , which are well-described by a single blackbody with effective temperature K. Comparing the phase curves to the predictions of one-dimensional and three-dimensional atmospheric models, we find that WASP-19b's dayside emission is consistent with a model atmosphere with no dayside thermal inversion and moderately efficient day-night circulation. We also detect an eastward-shifted hotspot, suggesting the presence of a superrotating equatorial jet. In contrast, HAT-P-7b's dayside emission suggests a dayside thermal inversion and relatively inefficient day-night circulation; no hotspot shift is detected. For both planets, these same models do not agree with the measured nightside emission. The discrepancies in the model-data comparisons for WASP-19b might be explained by high-altitude silicate clouds on the nightside and/or high atmospheric metallicity, while the very low 3.6 m nightside planetary brightness for HAT-P-7b may be indicative of an enhanced global C/O ratio. We compute Bond albedos of 0 ( at ) and for WASP-19b and HAT-P-7b, respectively. In the context of other planets with thermal phase curve measurements, we show that WASP-19b and HAT-P-7b fit the general trend of decreasing day-night heat recirculation with increasing irradiation.

22 pages, 29 figures, accepted by ApJ

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