It was great to have John Johnson (Harvard), Andrew Vandenburg (Harvard), Ben Montet (Harvard), and Ruth Angus (Oxford & Harvard) all at CampHogg group meeting today! Each of these brought results to discuss. Vandenburg blew us away with a two-planet system discovered in the K2 data that is in a 3:2 resonance, but so precisely lined up with our line of sight that the transits are almost perfectly coincident in time! Incredible; so unlikely that we discussed the possibility that one of the bodies is an artificial planet placed there by the alien technologists to send us a signal! Johnson showed us an binary-star gravitational lens that is so close, all components can be spectroscopically monitored to compare lens-based inferences with radial-velocity inferences. Perfect agreement!
After show-and-tell, Montet and Foreman-Mackey discussed the state of their K2 search-and-characterization work, and the scope of the first paper, which they spent the rest of the day working on. One thing they mentioned was a brilliant idea from Tim Morton (Princeton) to look for what are known as "astrophysical" false positives: Apply their exoplanet transit depth measurement method not just to the brightness of the star, but also to the x and y position measurements of the star: If the transit appears (gets a finite "depth") in the position measurements, then it is probably a blend with a background star. Beautiful idea.
Along those same lines, we discussed the relationship between the systematics removal of Dun Wang and Foreman-Mackey (using stars to model stars) and that of Vandenburg (using centroid measurements to model stars) and how they are different and the same. I made my counter-intuitive point that the centroid of a star might be encoded at higher signal-to-noise in its brightness than in its actual, direct centroid measurements! This is related to my Kepler-thermometer project idea.
We spent the rest of the day hacking, on exoplanets, writing, and asteroseismology.