I started the day working on the title and abstract of the mature draft that Alex Malz is getting ready for submission. It is on the responsible use of probabilistic redshifts. As I often say, it is the title and abstract that are the most important parts of a paper. We don't usually spend enough time on either. I had things to say about both in this case.
In the middle of the day, Kat Deck (Caltech) gave a great talk at NYU about exoplanet dynamics. She spent half her time on her very clever analyses (and simplifications of) planet–planet interactions as revealed by transit timing variations. She has a canonical transformation that takes the problem to action–angle coordinates. The cool thing is that the variations are an aperiodicity, and in action–angle coordinates everything is completely periodic, so the canonical transformation transforms away the variations! She spent the second half of her talk on long-term orbital stability of planetary systems, showing some examples that are close to the limits of what's expected (from resonance overlap arguments) to be stable. If pairs of planets are found at similar periods and with large enough masses, Deck can show that they have to be trapped in a resonance. Her talk was a great mix of theory and phenomena, in the rich subject area of exoplanets. She also made some comments at the end about using these kinds of techniques to understand gravitational wave systems.
Late in the day I visited Ellie Schwab (CUNY) and Kelle Cruz (CUNY) to discuss Schwab's project to measure the flaring rates of low-mass stars as a function of effective temperature. David Rodriguez (AMNH) also helped us out. We discussed a possible likelihood function that makes use of the magic of Gaussians to make everything tractable and fast.