The bugbear of extreme precision radial velocity measurements is often called “stellar activity”. I don't love that terminology, because stellar activity has a magnetic-field-reconnection feel to it, when the thing being referenced really covers all sorts of stellar variability that maps onto radial-velocity measurements. Today, Bedell (Flatiron), Zhao (Yale), and I discussed how we are going to approach a stellar activity challenge coming from the EXPRES group at Yale: They have released spectra for many epochs of observing from one star, and the team that delivers the best RV precision wins. Wins? Well, has some bragging rights.
Our plan is to look for spectral changes that predict velocity changes. That is, can we see different spectra on different parts of the stellar surface and relate those to measured and true velocities? We discussed the stellar rotation period, photometric variations, and classical activity indicators, all of which might help us in our goals.
The first order of business? Get wobble to run on the spectra, and make it deliver residuals away from the best constant-star fit.
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