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Keywords:

  • stars: individual: WASP-33;
  • stars: oscillations;
  • planetary systems;
  • stars: variables: δ Scuti;
  • infrared: planetary systems

ABSTRACT

We report ground-based observations at 0.91 μm of the occultation of the hot Jupiter WASP-33b by its A5 host star. We measure the planet to be 0.109 ± 0.030 per cent as bright as its host star at 0.91 μm. This corresponds to a brightness temperature, TB= 3620+200− 250 K, significantly higher than the zero-albedo equilibrium temperature for both isotropic re-radiation (2750 ± 37 K) and uniform day-side-only re-radiation (3271 ± 44 K), but consistent with the zero-redistribution temperature (3515 ± 47 K). This indicates that the heat redistribution from the day side of WASP-33b to the night side is inefficient and further suggests that there is immediate re-radiation, and therefore little or no redistribution, of heat within the day side. We also detected the stellar pulsations of WASP-33, which we model as the sum of four sinusoids, with periods of between 42 and 77 min and amplitudes of 0.5–1.5 mmag.