Lily Zhao (Yale) showed new regression results to Megan Bedell (Flatiron) and me today. She's asking whether shape properties of a stellar spectrum give you any information about the radial velocity of the star, beyond the Doppler shift. The reason there might be some signatures is that (for example) star spots and pulsations can distort radial-velocity measurements (at the m/s level) and they also (very slightly) change the shape of the stellar spectrum (line ratios and line shapes and so on). She has approaches that are \emph{discriminative}—they try to predict the RV from the spectrum—and approaches that are \emph{generative}—they try to predict the spectrum from the RV and other housekeeping data. Right now the discriminative approaches seem to be winning, and they seem to be delivering a substantial amount of RV information. If this is successful, it will be the culmination of a lot of hard work.
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