I spent science time today and yesterday reading carefully a nice new manuscript by Leslie Rogers (Caltech) about the densities of exoplanets as a function of mass. She can show with confidence that super-Earths larger in radius than about 1.6 Earth Radii are not rocky; they must have volatiles (water or worse) contributing to their effective (as measured by transits in the optical) radii. The data on these tiny planets (especially the masses) are extremely noisy, so she used hierarchical inference to get the noise-deconvolved density distribution, following the advice in this paper. The SAMSI program Eric Ford organized last summer is definitely getting me some citations for that paper!
In other news, Fadely showed me awesome results from his data-driven model for the HST WFC3 point-spread function. Does anyone have any model (other than TinyTim) against which we can compare?