chemical abundances in APOGEE and GALAH

In a full day at MPIA in Heidelberg, I spoke at length with Jan Rybizki (MPIA) and Sven Buder (MPIA), along with Hans-Walter Rix and Melissa Ness. Jan's project is to work on nucleosynthetic models; he has upgraded his code to generate what I call “shot noise”—the noise arising from the fact that in small star-formation regions, the number of supernovae can be small enough such that chemical enrichment does not approach the expected mean. We discussed first papers, observing that many of our plans could be executed with just the Sun and Arcturus and a few other standards; we need accuracy more than we need numbers for many first projects. My first project with Rybizki's code is to look at chemical-abundance diversity. I'd like to pose a well-posed question that makes use of the power of APOGEE.

Buder's project is to produce chemical-abundance labels for GALAH spectra using The Cannon. The problem, as per usual, is to obtain a good training set. We discussed the SME code that he is using and how we could wrap it or repurpose it. He showed us a beautiful set of results that show that when a star in GALAH gets low likelihood under the trained model of The Cannon, it is almost always interesting: A binary, a fast rotator, or maybe even a white dwarf.

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