detailed abundances and stellar companions

Taisiya Kopytova arrived in NYC for a few days to work on stellar abundances and orbital companions. Her project is very well designed: She has a set of red-giant stars in APOGEE where we know they have companions. For each of these stars with companions, she has found a set of matched stars—matched in stellar parameters—that don't have companions (or not companions that are detectable). She then compares the detailed chemical abundances between these two samples. The approach is extremely conservative and very robust to problems in the data: For a false effect to appear, it has to be an effect that causes a companion to be detected (or not detected)! And she finds signals.

One disturbing thing is that we find signal-to-noise effects, and we get slightly different results when we use APOGEE DR13 or DR14 data. So we might need to match on signal-to-noise as well as stellar parameters.

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