3.6 and 4.5 $\mu$m Phase Curves of the Highly-Irradiated Eccentric Hot Jupiter WASP-14b

TL;DR

This study presents detailed phase curve observations of the eccentric hot Jupiter WASP-14b at 3.6 and 4.5 micrometers, comparing models to reveal atmospheric composition, temperature structure, and heat redistribution.

Contribution

First full-orbit phase curves of WASP-14b at these wavelengths, with analysis of atmospheric models and implications for composition and heat emission.

Findings

Measured secondary eclipse depths consistent with a 2402 K blackbody.

Nightside flux is less than 10% of dayside flux at 3.6 μm.

Phase curves suggest lower albedo and deep heat emission.

Abstract

We present full-orbit phase curve observations of the eccentric ($e\sim 0.08$) transiting hot Jupiter WASP-14b obtained in the 3.6 and 4.5 $\mu$m bands using the \textit{Spitzer Space Telescope}. We use two different methods for removing the intrapixel sensitivity effect and compare their efficacy in decoupling the instrumental noise. Our measured secondary eclipse depths of $0.1882\%\pm 0.0048\%$ and $0.2247\%\pm 0.0086\%$ at 3.6 and 4.5 $\mu$m, respectively, are both consistent with a blackbody temperature of $2402\pm 35$ K. We place a $2\sigma$ upper limit on the nightside flux at 3.6 $\mu$m and find it to be $9\%\pm 1\%$ of the dayside flux, corresponding to a brightness temperature of 1079 K. At 4.5 $\mu$m, the minimum planet flux is $30\%\pm 5\%$ of the maximum flux, corresponding to a brightness temperature of $1380\pm 65$ K. We compare our measured phase curves to the predictions of one-dimensional radiative transfer and three-dimensional general circulation models. We find that WASP-14b's measured dayside emission is consistent with a model atmosphere with equilibrium chemistry and a moderate temperature inversion. These same models tend to over-predict the nightside emission at 3.6 $\mu$m, while under-predicting the nightside emission at 4.5 $\mu$m. We propose that this discrepancy might be explained by an enhanced global C/O ratio. In addition, we find that the phase curves of WASP-14b ($7.8 M_{\mathrm{Jup}}$) are consistent with a much lower albedo than those of other Jovian mass planets with thermal phase curve measurements, suggesting that it may be emitting detectable heat from the deep atmosphere or interior processes.