Aarhus Universitets segl

SAC Seminar - Karsten Frank Brogaard: Properties of the Hyades, the eclipsing binary HD27130, and the oscillating red giant ε Tau

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Torsdag 4. februar 2021,  kl. 10:30 - 11:30



Eclipsing binary stars allow derivation of accurate and precise masses and radii. When they reside in star clusters, properties of even higher precision, along with additional information, can be extracted. Asteroseismic investigations of solar-like oscillations offers similar possibilities for single stars.

We improve the previously established properties of the Hyades eclipsing binary HD 27130 and re-assess the asteroseismic properties of the giant star epsilon Tau. The physical properties of these members of the Hyades are then used to constrain the helium content and age of the cluster. We find that for epsilon Tau, the Hipparcos parallax is more reliable than the Gaia DR2 parallax. The helium content of HD 27130 and thus of the Hyades is found to be Y = 0.27 but with significant model dependence. Correlations with the adopted metallicity results in a robust helium enrichment law with ?Y/?Z close to 1.2 We estimate the age of the Hyades to be 0.9 ± 0.1 (stat) ± 0.1 (sys) Gyr in tension with recent age estimates based on the cluster white dwarfs. The age precision can be much improved by asteroseismic of the other Hyades giants, and by future improvements to the Gaia parallax of bright stars. I propose a new joint SAC SONG project for asteroseismology of the other Hyades giants for anyone interested.Title: Properties of the Hyades, the eclipsing binary HD27130, and the oscillating red giant ? Tau.

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