rodrigo's blog

A blog about astronomy, stars, exoplanets, data analysis, Bayesian statistics, open source code development, and other random thoughts that pop into my head.

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Synthetic Likelihoods

Rodrigo Luger October 27 2020

In this post I dig a little deeper into the assumptions I'm making when I try to model stellar surfaces (and, equivalently, stellar light curves) using a Gaussian Process. The true likelihood function for the data is certainly not a gaussian, but it turns out that approximating it as such is not a terrible idea. Here I'll discuss the concept of a synthetic likelihood, which is a term from the ecology literature (and is probably called different things in different fields), and explore its behavior with a very simple toy model. I'll warn you right now that I'm in a bit over my head with this, so comments / thoughts from proper statisticians are most welcome!

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Interpretable GPs for stellar rotation (Part 2)

Rodrigo Luger October 1 2020

This is a continuation of the previous post, in which we implemented a very slow, inefficient, and numerically unstable Gaussian process for stellar light curves. In this post I'll discuss how to compute the GP kernel analytically and show how to use this GP to learn about star spot properties from stellar light curves.

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Interpretable GPs for stellar rotation (Part 1)

Rodrigo Luger September 24 2020

As I discussed in my previous post, the information content of stellar light curves can be exceptionally tiny, owing to the large number of degeneracies when projecting from a two-dimensional space (the stellar surface) to a one-dimensional curve (the flux timeseries). Instead of trying to produce a definitive map of a stellar surface from a light curve, we can instead model the surface as a statistical process. In this post, I discuss ongoing work to develop a Gaussian process for stellar light curves whose hyperparameters are rooted in statistical properties of the stellar surface.

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So I started a blog...

Rodrigo Luger September 17 2020

Ever since I started my postdoc at the CCA, it feels like I've started a million different projects (and finished none). I have a lot of half-finished (or more like half-baked) ideas that I felt I had to write down somewhere, so I decided to start a blog! This blog will be a mishmash of posts on astronomy, data science, math, and any other random thoughts that pop into my head.

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