WASP-76 CHEOPS light curves

We also report the analysis of three unpublished sectors observed by the tess space telescope (also in the visible), which represents 34 phase curves. Results: WASP-76 b displays an occultation of 260+/-11 and 152+/-10ppm in tess and cheops bandpasses respectively. Depending on the composition assumed for the atmosphere and the data reduction used for the IR data, we derived geometric albedo estimates that range from 0.05+/-0.023 to 0.146+/-0.013 and from <0.13 to 0.189+/-0.017 in the cheops and tess bandpasses, respectively.

As expected from the IR phase curves, a low-order model of the phase curves does not yield any detectable asymmetry in the visible either. However, an empirical model allowing for sharper phase curve variations offers a hint of a flux excess before the occultation, with an amplitude of ~40 ppm, an orbital offset of ~-30 degrees, and a width of ~20 degrees. We also constrained the orbital eccentricity of WASP-76 b to a value lower than 0.0067, with a 99.7% confidence level.

This result contradicts earlier proposed scenarios aimed at explaining the asymmetry observed in high-resolution transit spectroscopy. In light of these findings, we hypothesise that WASP-76 b could have night-side clouds that extend predominantly towards its eastern limb. At this limb, the clouds would be associated with spherical droplets or spherically shaped aerosols of an unknown species, which would be responsible for a glory effect in the visible phase curves.