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Paper: Improved Opacities and Pulsation Models for sdB and sdO Stars
Volume: 392, Hot Subdwarf Stars and Related Objects
Page: 245
Authors: Jeffery, C.S.; Saio, H.
Abstract: We have reconsidered the excitation of radial and non-radial oscillations in models of low-mass early-type stars by the so-called iron-bump opacity mechanism. Our models provide an indication of stability and periods for low-order radial and non-radial p- and g-modes. They are important for understanding pulsations in subluminous B and O stars and other evolved stars of low-mass.

Recent work by the Opacity Project showed that the position of the opacity peak due to iron-group elements occurs at higher temperatures than previously thought. At these temperatures and solar abundances, nickel contributes nearly as much opacity as iron. The new opacities can better match the observed distribution of V361Hya (=EC14026–2647) stars with iron and nickel enhanced by a factor ∼ 4. They also provide a better match to the observed blue edge of the V1093Her (=PG1716+426) instability strip.

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