FM17p.02 — The chemical composition of β Cephei and hybrid pulsators in the solar neighbourhood

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Aug 10th at 6:00 PM until 6:00 PM

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Author(s): Norbert Przybilla1, Maria-Fernanda Nieva1

Institution(s): 1. University of Innsbruck

β Cephei variables are the most prominent pulsators among the massive stars on the upper main sequence, extending into the class of the rare hybrid β Cephei-SPB pulsators in the overlap region with the instability strip of the Slowly Pulsating B-stars. While the κ-mechanism has been identified as the driver of the pulsations, a comprehensive explanation of the excitation of the observed p- and g-modes is still lacking. In particular, the instability regions for these main-­sequence B-type pulsators are still not fully consistent with any current opacity calculations.

We have determined tight observational constraints on the chemical composition of a sample of β Cephei and hybrid pulsators in the solar neighbouhood, covering all elements with abundances log(X/H)+12>7.3. The star sample turns out to be chemically homogeneous, with a metallicity Z≈0.014. The availability of accurate and precise abundances eliminates one of the two variables in the opacity calculations for asteroseismic applications, allowing to focus on (missing) atomic data.