S316.12.05 — Looks like a duck, moves like a duck, but does it quack like a duck? Asteroseismology of red-giant stars in clusters

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Aug 14th at 12:00 PM until 12:20 PM

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Author(s): Andrea Miglio2, Karsten Brogaard1, Rasmus Handberg1

Institution(s): 1. University of Aarhus, 2. University of Birmingham

Undoubtedly one the highlights of the Kepler asteroseismology programme has been the detection of solar-like oscillations in giants belonging to the open clusters NGC 6791, NGC 6819, and NGC 6811. The availability of such constraints has made it possible to infer precise stellar properties (e.g. radius, mass, evolutionary state, age) on a star-by-star basis.
These constraints give us a “new pair of eyes” to look at clusters, and they open several exciting opportunities. Based on a detailed analysis of the complete set of 4-years-long Kepler data, we present clear evidence for stars that have undergone non-standard evolution (evolved blue stragglers, low-mass Li-rich stars). We then illustrate the potential of integrated-mass-loss and mass-loss-dispersion measurements in both NGC6791 and NGC6819, which suggest a small true mass scatter among the red-clump stars and thus a very small mass-loss dispersion.
We will then show examples of how our analysis based on individual-mode frequencies, as opposed to average seismic parameters and scaling relations, allow us to determine with higher accuracy stellar properties, and to probe features in the deep stellar interior (i.e. acoustic glitches related to Helium ionisation, properties of near-core mixing in the He-core-burning phase).
Finally, we will discuss the prospects for seismic analyses of other clusters, in particular the globular cluster M4 which could reveal new insights into mass-loss dispersion and its effect on the horizontal-branch morphology.