The day started with a long call with Adrian Price-Whelan (Princeton) regarding binary-star systems, their detection and analysis. We discussed the oddities we are finding in Gaia TGAS. This led to a call later in the day with Semyeong Oh (Princeton), who showed us really nice results. We definitely see the Gaia DR1 exposure map in the sky positions of our detected binaries, but this is as expected: We are more sensitive where we have better data! I am starting to think that we have a reliable catalog. Also on that call we found this highly relevant paper from the Hipparcos era.
Later in the day, Dustin Lang (Toronto) and I discussed my project (which is constantly shrinking in scope) to build a data-driven, noise-deconvolved model of the color–magnitude distribution of stars in TGAS. He endorsed the very simple project and had some good ideas. I now think I might actually have a do-able project for the #GaiaSprint. It also fits in to things that Lang and I have been saying for years, about shrinkage and hierarchical thinking.