2019-02-13

stars, dark matter, TESS

Today at Flatiron, Adrian Price-Whelan (Princeton) gave a very nice talk about using stars to infer things about the dark matter in the Milky Way. He drew a very nice graphical model, connecting dark matter, cosmology, and galaxy formation, and then showed how we can infer properties of the dark matter from stellar kinematics (positions and velocities). As my loyal reader knows, this is one of my favorite philosophical questions. Anyway, he concentrated on stellar streams and showed us some nice results on Ophiucus and GD-1 (some of which have my name on them).

The weekly Stars Meeting at Flatiron was great today. Ben Pope (NYU) showed us some terrific systematic effects in the NASA TESS data, which leads to spurious transit detections if not properly tracked. Some of these probably relate to Earthshine in the detector, about which I hope to learn more when Flatiron people return from the TESS meeting that's on in Baltimore right now.

In that same meeting, Price-Whelan showed us evidence that stars lower on the red-giant branch are more likely to have close binary companions (from APOGEE radial-velocity data). This fits in with an engulfment model (as red giants expand) but it looks like this effect must work out to pretty large orbital radius. Which maybe isn't crazy? Not sure.

And Jason Curtis (Columbia) showed amazing stellar-rotation results from TESS data on a new open cluster that we (Semyeong Oh et al) found in the ESA Gaia data. He can show from a beautifully informative relationship between rotation period and color (like really tight) that the cluster is extremely similar to the Pleiades in age. Really beautiful results. It is clear that gyrochronology works well for young ages (I guess that's a no-brainer) and it is also clear that it is way more precise for groups of stars than individuals. We discussed the possibility that this is evidence for the theoretical idea that star clusters should form in clusters.

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