Andy Casey had the afternoon off from #FirstStarsV; that and the presence of Adrian Price-Whelan inspired me to suggest that we structure the afternoon like a hack day, in an undisclosed garden location in the Heidelberger Neuenheim. We were joined by Christina Eilers (MPIA), Melissa Ness (MPIA), Hans-Walter Rix, Branimir Sesar (MPIA), and Gail Zasowski (JHU). Various projects were pitched and executed. My own work was on my response-to-referee (boring I know!) and helping Eilers with coding up the objective function and derivatives for a version of The Cannon that permits the inclusion of stars with noisy and missing labels at training time. Casey worked on building giant-branch and main-sequence Cannon models and mixing them or switching between them. It appears to work amazingly well.
In the morning before that, MPIA Milky Way group meeting hosted a discussion by Price-Whelan of the possibility of understanding what original population of globular clusters was ground up and stripped into the present-day Milky-Way halo, and a discussion by Andy Casey of an amazingly low metallicity, amazingly rapidly moving star, that appears to have just fallen in from somewhere. These led to excited discussions, and, indeed, framed some of the projects performed at the above-mentioned hack day. For example, at the hack day, Price-Whelan made predictions for other stars that might be part of whatever cluster, group, or galaxy fell in with Casey's crazy star.