graphical models; bugs

At MPIA MW group meeting, Semyeong Oh (Princeton) described her projects to find—and follow up—co-moving stellar pairs and groups in the Gaia TGAS data. She presented the hypothesis test (or model comparison) by showing the two graphical models, which was an extremely informative and compact way to describe the problem. This led to a post-meeting discussion of graphical models and how to learn about them. There is no really good resource for astronomers. We should write one!

I spent the afternoon with Matthias Samland (MPIA) and Jessica Birky (UCSD), debugging code! Samland is adding a new kind of systematics model to his VLT-SPHERE data analysis. Birky is hitting the limitations of some of our code that implements The Cannon. I got a bit discouraged about the latter: The Cannon is a set of ideas, not a software package! That's good, but it means that I don't have a perfectly reliable and extensible software package.

nuisance model for imaging

The CPM of Wang et al and the transit search methods of Foreman-Mackey et al were developed by us to account for and remove or obviate systematic issues with the Kepler imaging. Last summer, Matthias Samland (MPIA) pointed out that these could be used in direct imaging of exoplanets, which is another place where highly informative things happen in the nuisance space. Today we worked through the math and code that would make a systematics-marginalized search for direct detections of planets in the VLT-SPHERE imaging data. It involves finding a basis of time variations of pixels in the device (pixels, not patches, which is odd and at odds with the standard practice), choosing a prior on these that makes sense, fitting every pixel in the relevant part of the device as sum of variations plus exoplanet, but marginalizing out the former.