star spots and exoplanets; mapping the disk

Today in MPIA/LSW Stars Meeting Néstor Espinoza (MPIA) gave a nice presentation about how star spots (cool spots) and faculae (hot spots) on stellar surfaces make it difficult to simply extract an exoplanet transit spectrum from differences between in-transit and out-of-transit spectra of the star. Some of the issues are extremely intractable: Even spectral monitoring of the star might not help in certain geometries. But we did agree that space-based spectral monitoring could do a lot towards understanding the issues. He showed that some of the transit-spectrum results in the literature are likely wrong, too. One conclusion: Gaia low-resolution spectrophotometry as a function of transit epoch at Gaia DR4 or thereabouts might have a lot to say here! And I also thought: SPHEREx!

After weeks of writing, today I finished the zeroth draft (yes, it isn't even close to being ready for anything) of the paper about our spectrophotometric parallax model for luminous red giant stars with Eilers (MPIA). I will get it into a state that I can share it with the APOGEE team this week.

And Eilers made maps of kinematic evidence of non-axi-symmetry in the Milky Way disk and radial abundance gradients, using our luminous red giants. We have lots of issues of interpretation, but there are a lot of things here. In my spare brain cycles I figured out a way that we could use Eilers's results to calibrate the variations of the inferred stellar abundances as a function of effective temperature and surface gravity: We can see that the data have issues.

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