Emergent spectral IR fluxes of 122 hot Jupiters

To achieve a large and uniform sample, we have reanalyzed all secondary eclipses for all hot Jupiters observed by Spitzer at 3.6 and/or 4.5{mu}m. Our sample comprises 457 eclipses of 122 planets, including eclipses of 13 planets not previously published.

We use these eclipse depths to calculate the spectral fluxes emergent from the exoplanetary atmospheres, and thereby infer the temperatures and spectral properties of hot Jupiters. We find that an abrupt rise in brightness temperature, similar to a phase change, occurs on the dayside atmospheres of the population at an equilibrium temperature between 1714 and 1818K (99% confidence limits). The amplitude of the rise is 291{+/-}49K, and two viable causes are the onset of magnetic drag that inhibits longitudinal heat redistribution, and/or the rapid dissipation of dayside clouds.