My only real research today was a conversation with new NYU graduate student Shengqi Yang, who is going to start on a project to look at binary stars in the APOGEE data as linear combinations of single stars. That is, a purely empirical model (for now). We discussed how to find similar stars, and how to decide that they are similar, and what a binary star would look like in the continuum-normalized spectral space. The nice thing about the problem is that, in principle, a search for binaries among N spectra might take N3 time, since any star could be a mixture of any two others! However, we are going to start with the Gaia TGAS overlap, which reduces the numbers an also trims the tree, because there are many triples that—given what we know from Gaia—couldn't be so related.